In October 2014, the Guardian journalist Seumas Milne arrived in the Russian city of Sochi on the Black Sea coast, near the Georgian border. He was there to attend the annual Valdai international discussion club where Russia experts from across the world – academics, diplomats, journalists – meet and sometimes question President Vladimir Putin and some of his top officials and advisers. The theme of that year’s conference was “The World Order: New Rules or No Rules?”. Milne, his expenses paid by the Russian business people who organise the event and started it a decade earlier, was there to talk about the Middle East, a subject of which he has compendious knowledge, derived from a lifetime interest in the region.

To his surprise, Milne was asked, while in Sochi, to chair the meeting’s key session, where Putin was to make a 40-minute speech – later described by the Financial Times as one of his “most important foreign policy statements” – followed by a lengthy question-and-answer session. Milne agreed and opened the questions by asking two of his own. Were Russia’s “actions in Ukraine and Crimea” (which Moscow had recently invaded) “a response to [a] breakdown of rules and a sort of example of a ‘no-rules’ order”? And would Russia alter its position that, following the collapse of the Soviet Union, it “can’t lead in the current global order but it can decide who leads”?

Innocuous as the questions may have seemed, controversy over Milne’s role at Valdai followed quickly, particularly at the Guardian. Like a number of other British and American critics of Putin, leading figures on the paper’s foreign desk argued that, after the invasion of Crimea, it was no longer acceptable for Westerners to attend Valdai. These people were legitimising an aggressive and authoritarian regime that paid little regard to human rights. Valdai was aimed solely at projecting the Kremlin line.

On the left-wing blog Left Foot Forward, Pierre Vaux, a writer closely associated with a New York think tank set up by anti-Putin exiles, argued that Milne was performing “front-of-house PR duties” with the president. Milne had long been a Kremlin “fellow-traveller”, Vaux said; now he was behaving like “a direct advocate, an agent of influence”. His questions allowed Putin “the space to not only justify Russian actions in Ukraine . . . but also to grandstand about Russia’s humble and well-meaning place in the world”. Vaux pointed out that, a few days after his visit to Sochi, Milne’s weekly Guardian column blamed the crisis in Ukraine on the US and the EU backing “the violent overthrow of an elected if corrupt government”.

Vaux stirred the pot by quoting the Guardian’s former Moscow correspondent Luke Harding as saying that to attend Valdai was to become “a puppet in the Kremlin’s theatre, there to make Putin look good”. The row spilled over into the paper’s offices in King’s Cross, London. Milne and Harding exchanged angry emails. When Harding – who has published a book about Putin’s Russia called Mafia State as well as accounts of how he was harassed during his four-year spell in Moscow – wrote that the Kremlin was guilty of funding far-right groups in Europe, they clashed at one of the paper’s daily editorial conferences. Milne’s mobile phone rang in the middle of the exchange. “That must be the Kremlin,” joked Harding, which, far from defusing the tension, took it to new levels. Voices were raised and the two men clashed in the newsroom and even the urinals after the meeting. “We don’t normally have angry words at the Guardian,” a shocked witness told me later.

There the matter might have rested, with the controversy, dismissed by many journalists as a turf war between writers jealous of their territory, confined to little-read online publications and of interest only to Russia specialists. But a year after he went to Sochi, Milne was appointed director of strategy and communications for the Lab­our Party’s new leader, Jeremy Corbyn. The national press took a sudden interest in his attendance at the Valdai meeting. “Red handed!” screeched the Mail, showing photographs of Putin shaking Milne’s hand and watching sternly as the columnist invited questions. “Corbyn’s pro-Kremlin spin chief held in Putin’s iron grip at propaganda summit.” Milne was bizarrely criticised for not interrogating Putin as Jeremy Paxman would have interrogated a British politician.

Milne had become another target in the press assault on Corbyn and his supporters, mounted mostly, but not entirely, by right-wing papers. After more than ten years of writing columns from a firmly left-wing viewpoint, many of them about international issues, Milne provided ample ammunition. He had argued that the killing of Lee Rigby, “a British soldier who had taken part in multiple combat operations in Afghanistan . . . wasn’t terrorism in the normal sense of an indiscriminate attack on civilians”. Two days after the 9/11 attacks, in an article that attracted a record 6,000 readers’ emails (roughly divided evenly for and against him), Milne wrote that Americans were “reaping a dragons’ teeth harvest they themselves sowed”. After 7/7, he claimed that the London bombings were “driven by worldwide anger at US-led domination and occupation of Muslim countries” and, given that Britain was a firm supporter of the US, the only surprise was that they had been “so long coming”. At an anti-Israel rally in 2014, he said Palestinians in Gaza were not terrorists: “the terrorism is the killing of civilians by Israel on an industrial scale”. And, according to Milne, Russia under Putin “provided some check to unbridled US power”.

Many such comments were wrenched out of context by right-wing papers. For example, Milne wrote of Lee Rigby that “the random butchery of an unarmed man far from the conflict by disconnected individuals who have non-violent political alternatives is clearly unjustifiable”. Nearly everything he has written about Putin describes him as authoritarian, conservative and definitely not “progressive”. Moreover, on the contribution of Western policies to terror attacks, views similar to Milne’s can be found across the Western political spectrum and even among senior diplomats and military figures, never mind across all sections of society in Africa and Asia.

Most newspaper columns are intended to surprise and provoke readers; predictable, orthodox, moderately expressed opinions are the province of politicians. Yet critics argue that Milne’s views are peculiarly hardline and extreme. Harding isn’t the only Guardian colleague with whom he has clashed. In October 2015, Brian Whitaker, the paper’s former Middle East editor, recalled on his blog al-bab.com a conversation with Milne in 1990 about the fate of Farzad Bazoft, a UK-based freelance journalist working in Iraq for the Observer. Bazoft, who had been making inquiries about a military site and taking soil samples nearby, was arrested and accused of being an Israeli spy working for the West. He was hanged on the orders of Saddam Hussein.

Whitaker was “startled when he [Milne] sought to justify Bazoft’s arrest” though not his execution. “He views international politics almost entirely through an anti-imperialist lens,” Whitaker wrote. That led him “to a sympathetic view of those dictatorial regimes which characterise themselves as anti-imperialist”. Milne, Whitaker said to me recently, “regards the people who want liberty in the Middle East as mostly Western stooges” and “never seems to express any libertarian instincts at all, either of the left or the right”. Whitaker’s concern is that Milne’s view of Britain’s historic role in the Middle East is even less subtle than Corbyn’s. “Britain’s relationship with repressive (but West-friendly) regimes,” Whitaker wrote last year, “and the Cameron government’s apparent determination to prioritise trade – including arms sales – over human rights are issues that desperately need serious public debate . . . Corbyn has shown a commendable willingness to raise them.” But can he do that with credibility “when his spin doctor has shown so much sympathy for anti-Western regimes that have been no less repressive”?

Similar questions are common even among those broadly sympathetic to Corbyn. Are Milne’s opinions too consistently and uncompromisingly left-wing? Does “the Thin Controller”, as he is known at the Guardian, have a sufficiently flexible mind to persuade Corbyn to fine-tune his message and make the compromises necessary in front-line politics? Can he help the Labour leader appeal to a wider audience? Does he even want to?

***

Milne is a clever man. Nobody I spoke to doubted that, though one source added that “he has little wisdom”. He is also well read, with several enormous filing cabinets at the Guardian, of the sort banished from most newspaper offices decades ago, full of books, reports and pamphlets. His desk was covered with a mountain of paper visible from the opposite side of the office which, from time to time, would slide slowly towards his neighbours. “He’s often the best-informed person in the room on any subject,” said a Guardian colleague. “He knows a lot of history and could probably walk you through all the prime ministers of Israel since 1948 without missing a beat. The knowledge is almost scholarly.” But the other side of him, said the same colleague, is that “he cherry-picks what he reads in an almost unintelligent way; he has a closed mind and an unpersuadable one”.

Another colleague at the Guardian told me: “Seumas is one of the most wholly political people I’ve ever met. He thinks of everything politically. He has a project and it’s political, not journalistic.” A third Guardian journalist said that his written output for the paper was never large. When he became a columnist, he rarely wrote more than one column a week. “He got a reputation for laziness. But I think that’s unfair. It’s just that he was doing other things, political things.” A fourth source said: “He sees himself as an activist who happens to work for a newspaper. He will tell you something and you’ll say ‘that’s a good story’ but he won’t write it for the paper because it wouldn’t go down well with the comrades.”

Some journalists saw him as a slightly sinister, furtive, cold figure, always pacing the corridors while on his mobile phone, talking almost daily to his close friend George Galloway, whom he addressed as “chief”. One colleague described him as “a natural plotter”, never happier than when taking part in a caucus or cabal. Older hands recall his leading role in the Gulshan group in the early 1990s, named after an Indian restaurant where members met to plan resistance to what they saw as a rightward, downmarket drift at the Guardian. When, around the same time, an obscure magazine called Casablanca, now defunct, ran a scathing anonymous critique of how the Guardian was abandoning its liberal-left heritage, Milne was widely suspected as the main informant, particularly when his friend Tariq Ali confessed to being the author. Others recall his curious closeness to Peter Mandelson, the two apparently brought together by a love of plotting and a mutual loathing of Gordon Brown.

But colleagues also emphasise Milne’s charm and his calm, rather understated manner. “He nearly always sounds reasonable and sensible,” a colleague said. “He’s not a coiled spring waiting to have a row, like most people on the left.” Some said they thought a more human, caring side emerged after he took time off work to have a tumour removed from a lung and when, in 2013, his sister, Kirsty, a former New Statesman journalist, died at 49 from lung cancer. Many journalists acknowledge with gratitude his role in maintaining the Guardian chapel (union branch), which he led for many years, as one of the strongest in the industry, with a house agreement that still rules out compulsory redundancies. “The management always knew that, if ­necessary, he could deliver a strike,” said one.

Gary Younge, one of Milne’s closest friends on the paper, says: “Having been a Trot at 15, for a short period, I have some experience of rigid and doctrinaire socialists. Those are the people I find tiresome and boring. Seumas isn’t one of those. If you’re having an argument, he will engage with it, respond to what you’re saying.”

Becky Gardiner, who was also close to Milne at the Guardian and is now a lecturer in journalism at Goldsmiths, University of London, said: “Seumas is completely upfront about what he thinks. It’s ridiculous to accuse him of being secretive. When he talks on his mobile, it’s in a very loud voice. You know exactly who he’s talking to and what about.”

She, Younge and several other journalists agree that although his writing is hardly a bundle of fun and rarely contains a personal anecdote, Milne in person is nothing like the humourless leftist of popular caricature. “When you have a conversation with him,” Gardiner said, “you laugh a lot.” His friends are passionately loyal, perhaps surprisingly so, given his habit of arriving as much as an hour late for assignations. He has an impressive array of leftist contacts across the world, particularly in the Middle East and Latin America; in the past, they included Yasser Arafat and Hugo Chávez. “He’d always be coming into the office clutching an article for publication, saying something like, ‘This is from an excellent Turkish trade unionist,’” said a senior editor.

Outside politics, he seems to have little hinterland (his interest in sport is said to be zero) apart from popular music. He is awesomely knowledgeable about the Beatles and an enthusiast for the Rolling Stones; he also plays the guitar and sometimes the piano. He lives with his Italian wife, Cristina, in an Edwardian house in the leafy south-west London suburb of Richmond. Curiously, and not very ecologically, he usually drove to the Guardian’s offices and used the car throughout the day in London when he had a company parking space. Though Richmond’s state schools are wholly comprehensive, both of his children, now grown up, went to grammar schools in Kingston-upon-Thames, four miles away. Friends tell me that Milne – who declined to be interviewed for this article – refuses to discuss the subject but sometimes points out that the father isn’t the only member of a family who makes choices about the children’s education and that, in a truly democratic home, he can be comfortably outvoted.

If his own views have ever deviated from left orthodoxy on comprehensive schools – because he rarely writes or speaks about education, I could find no public statement of them – it would be a surprise. It is hard to discover any significant examples from the past 40 years of Milne changing his opinions, or even interrogating them. Born in 1958, he is a child of the 1970s, the last decade in which large numbers of people still believed that the near future belonged to socialism. “His political opinions stopped developing in 1975, along with his musical tastes,” was a colleague’s comment.

Milne’s cleverness won him a scholarship and a free place at Winchester, one of England’s most exclusive, cerebral and expensive fee-charging boarding schools, and later a scholarship place at Balliol, reputedly Oxford’s most intellectual college, to read philosophy, politics and economics.

As he left school, after taking his A-levels at 15 and his Oxford entrance exam at 16 – a common practice at Winchester – one-third of the world’s population was living under regimes that claimed to follow socialism in one form or another. In Britain, a Labour government had Michael Foot and Tony Benn in senior cabinet positions; raised the top rate on earned income to 83 per cent and that on investment income to 98 per cent; tried to control prices and incomes across the economy; nationalised British Leyland and established a National Enterprise Board. Many young Britons admired Mao Zedong and his “permanent revolution” in China. Many privately educated young people from elite backgrounds embraced revolutionary politics, as Milne did.

Not that his family was “establishment” in quite the conventional sense. His father, Alasdair, a producer at the BBC who became director general in 1982, was also a Wykehamist, but revelled in his Scottish roots, playing the bagpipes and speaking Gaelic. He was among the pioneers of a less deferential style at the BBC, and was sacked in 1987 largely because Margaret Thatcher thought that the corporation, under his command, was too biased in favour of the left. His wife, Sheila, Seumas’s mother, had an Irish-Danish background and was once an actor.

Though not a Tory, Alasdair Milne was certainly not a hardline left-winger. But nobody can remember his son being anything else. At Winchester, he stood as a Maoist in a mock election. The Conservative cabinet minister John Whittingdale, a contemporary of his at school, triumphantly produced printed evidence of this episode when Milne was appointed as an aide to Corbyn. He spent his gap year with friends in Lebanon, then in the throes of civil war. There, he learned Arabic, heard shots fired in anger, escaped from a blown-up building and was briefly captured by militiamen. Colleagues at the Guardian dismiss allegations that he attended a terrorist training camp as ludicrous. But he returned with a strong commitment to the Palestinian cause.

“He spent his entire time at Balliol,” a college contemporary recalls, “wearing a Mao jacket and talking with a fake ­Palestinian accent. It was like performance art, the sort of thing Gilbert and George would do. He launched a string of motions in the JCR [junior common room] attacking Israel.” (Guardian colleagues say he is still in the habit of adopting the accent of whoever he has most recently talked to.)

It was clear even then, both to Milne and to his fellow students, that he would devote his life to left-wing politics.

After leaving Oxford with a second-class degree, he went to Birkbeck College, University of London, to take an MA in economics, a subject he thought crucial to politics. He applied unsuccessfully to work for Labour’s Barbara Castle, who was generally considered to be on the left of the party, and for the TUC’s economics department.

Milne’s relationship with the Communist Party was close. After university, he did some work for a monthly journal called Straight Left, which, though most of its board members were left-wing Labour MPs and union leaders, became associated with the “Stalinist”, pro-Soviet, anti-Eurocommunist faction that eventually split from the Communist Party of Great Britain. It was through Straight Left that he met Andrew Murray, who became one of his closest friends. Murray, originally a Morning Star journalist, became the first chair of the Stop the War campaign when it was formed in 2001, and in 2011 was appointed chief of staff for the Unite trade union. Francis Beckett, who has written a book about the Communist Party and worked for several trade unions, described Murray to me as “extremely rigid and sectarian”. He added: “Murray and the Straight Left people were more extreme than most of the Stalinists I knew. The Stalinists were known as tankies, but Murray’s lot were super-tankies.”

Milne has always denied ever being a CP member but Beckett said “all the communists I know think he was in the party”. Whatever the truth – and there is no tangible evidence that he was a member – Milne had joined Labour by 1979. It was not then unusual, particularly in the union movement, for Labour supporters to work closely with Communists, whose discipline and organisation they admired and who shared a loathing of the “ultra-leftists” associated with various groups that went loosely under the label “Trotskyist”. Among those elected to the National Union of Students executive on the “Broad Left” ticket of Labour, Liberals and Communists was Charles Clarke, a future Labour cabinet minister.

It was not through left-wing connections that Milne secured his start in a Fleet Street career. In a textbook example of the British establishment at work, a highly-placed source told me Alasdair Milne (Winchester and New College, Oxford) recommended his son Seumas (Winchester and Balliol) to Andrew Knight (Ampleforth and Balliol), the then editor of the Economist. The young Milne stayed for three years, covering local government, education and the motor industry, but Knight, though he recognised Milne’s intellectual abilities, thought, rightly, that he was uncomfortable with the magazine’s free-market line. Knight went to his old and very close friend the Guardian columnist Hugo Young (Ampleforth and Balliol) and asked if the Guardian might be interested. The paper hired Milne in 1984.

***

Initially a general news reporter, Milne became a labour correspondent in 1990 and later the paper’s labour editor. His strong connections with union and Labour Party activists, what a Guardian colleague called “his unrivalled knowledge of the labour movement” and his own election in 1989 as a member of the National Union of Journalists executive council seemed to make him a perfect fit for the job. Moreover, he had recently written with two others – an academic who had been a contemporary at Balliol and a prominent figure in the Campaign for Labour Party Democracy, a pro-nationalisation pressure group – a book called Beyond the Casino Economy, which advocated extended “trade union statutory rights” and “a society based on common ownership where the working class and its allies hold political power”. In 1994 he published another book, The Enemy Within, showing how the British secret services infiltrated and set out to discredit the National Union of Mineworkers and its leader Arthur Scargill during the 1984-85 miners’ strike. Though widely regarded as too uncritical of Scargill – who gave Milne the co-operation he denied to most mainstream journalists – it was warmly reviewed, went through four editions (the latest of these in 2014) and is regarded by many journalists as an investigative classic.

By the mid-1990s, however, the labour brief began to look like a dead end. For one thing, Milne, seen as fastidious, aloof and slightly arrogant, did not get on well with some union leaders and labour correspondents. “He stuck out like a sore thumb among the labour correspondents who were the very opposite of a public school elite,” recalled Paul Routledge, who was then the labour editor at the Times. “He mixed with a select left strand of the union movement. He didn’t really get on, or want to get on with, the more hairy-arsed tendency. If he had met the miners I knew, who have some very old-fashioned ideas about life, he would have run a mile.” With Milne much sought after as a speaker at labour movement events, other correspondents joked that they would go to cover a conference and he would go to speak at it.

But there was a second, bigger problem. The trade unions were losing membership and influence; their leaders, particularly Scargill, were being marginalised. After the advent of New Labour in 1994, it became clear that, for the foreseeable future, they would have little role in mainstream British politics. The labour correspondents declined in parallel. A group that had once been a national reporting elite, second only to political reporters, dwindled in numbers and importance.

Several, including Routledge, eventually switched to covering politics in the Westminster lobby. It seemed likely that Milne would make a similar move at the Guardian. Instead, to the surprise of many colleagues, the Guardian editor Alan Rusbridger offered him a job that gave Milne potentially more influence over the direction of leftist debate and political thinking than he had ever enjoyed before.

Milne was comment editor of the Guardian from 2001 to 2007, supervising regular columnists such as Polly Toynbee, Jonathan Freedland and George Monbiot and inviting outsiders to contribute, among them politicians, academics and union leaders as well as journalists. These were the years when the Blairite project – anathema to Milne and his friends – began to unravel and Britain became sharply divided over the Iraq War. Yet, at first, colleagues were impressed with the spectrum of views he published, from right and left.

“He was meticulous about it,” said Becky Gardiner, who worked as his deputy for four years. “Whatever the issue, he broke it down into constituent parts, looked at all the angles and represented as many of them as possible in the pages.” He was particularly anxious to increase the number of female contributors, and insisted that there should be at least one a day. He also, said a colleague, kept a tally of pro- and anti-Israel articles “so that he could cover himself”.

Naomi Klein, the author of No Logo, hailed Milne’s achievement in turning the Guardian’s comment section into “a truly global debating forum”. More surprisingly, the Conservative MEP Daniel Hannan said he had made it “the most thought-provoking opinion section in Britain”.

Staff at the Guardian, however, are divided about Milne’s record as comment editor. As time went on and controversy over the Iraq War and Islamist terrorism grew, the number of Muslim radicals appearing in the pages increased. Left-wing friends such as Andrew Murray featured frequently. When the Blairite and pro-war columnist David Aaronovitch, recruited to the G2 section from the Independent in 2003, asked to move to the comment pages, Milne allegedly vetoed it and frequently referred (perhaps half jokingly, at least) to “the hated Aaronovitch”. Aaronovitch confirmed to me that his request, taken to the highest Guardian levels, was repeatedly ignored but said he had no idea whether or not Milne was responsible; he soon left for the Times. “Seumas put a lot of stuff into the paper that had no merit as writing,” said a senior Guardian figure. “Yes, he published right-wing people but they were usually iconoclasts who would say radical, surprising things and turned out to be against the Iraq War. He avoided the policy arguments taking place in the main parties.” His eclectic policies, critics thought, were just a way of making the publication of his far-left allies more acceptable.

The biggest row during Milne’s reign as comment editor came over his publication of an article by Osama Bin Laden, edited from one of the many taped statements the al-Qaeda leader put out, in 2004. An overwhelming majority of Guardian journalists thought the paper was right to publish the piece but a smaller majority thought it should not have been on the comment pages. Milne and his supporters insisted that its insights into what drove al-Qaeda justified its prominent position – particularly as Bin Laden’s views received wide attention across the Middle East – and that publishing opinions on the comment pages did not imply an endorsement of them. These arguments were backed by the Guardian’s readers’ editor, or ombudsman.

But by 2007 Milne’s critics had won. It was felt, I was told, that he was building up too many writers in his own mould and that he carried too many articles about Palestine. He was made associate editor and moved to writing a column, a weekly, rather lonely expression of views that had once represented a significant strand of mainstream left-wing opinion in Britain but had now apparently gone out of fashion for ever. Then came the call from Corbyn.

***

Dealing with Labour leaders was not entirely new to Milne. He and Ed Miliband had been friends for some years and, after Miliband was elected leader in 2010, Milne was among those consulted about his first party conference speech. The two continued to talk regularly, though less so as Milne became increasingly disappointed with Miliband’s lukewarm attitude towards fighting on a left-wing programme.

Corbyn knew Milne from the anti-war movement and in recent years had spoken with him at rallies and meetings. The two had also travelled together, with other MPs and activists, to Israel and Palestine. They were not, however, intimates. But when he became leader, Corbyn desperately needed somebody sympathetic to his views and also familiar with the mainstream media. Usually, a party leader comes to power with years of preparation, a firm base of parliamentary support, wide media experience and a trusted cohort of advisers. Corbyn had none of that: even his astonishingly successful campaign, primarily a social media operation, was organised by a group called Red Labour, spawned by a Facebook page started by a Brighton-based Labour activist whom Corbyn had never met. An infrastructure of union shop stewards, academics, the “peace movement”, union-financed research and constituency activists which had sustained Labour’s left in the early 1980s – and almost won the deputy leadership for Tony Benn – had all but disappeared over the following decades. The Labour Party staff largely dated from the Blair and Brown eras and their political thinking and loyalties echoed that. Corbyn knew almost nobody in the national press or broadcasting, even among the writers and reporters on the Daily Mirror and the Guardian.

His first approach was to Kevin Maguire, the New Statesman political diarist and Mirror associate editor. He turned Corbyn down as he had once turned down a position in Downing Street during Gordon Brown’s premiership. Milne also hesitated. Partly thanks to his assiduous campaigning, Katharine Viner had recently succeeded Rusbridger as Guardian editor. Viner, it was thought, might take the Guardian more to the left, though the paper backed Yvette Cooper, not Corbyn, in the 2015 Labour leadership election. Milne could reasonably expect to play a prominent and influential role in the new regime. Some friends advised him to turn down the offer, arguing that Corbyn couldn’t last.

But Milne felt an obligation to respond to a Labour leadership for which he had waited nearly all his life. Thanks to a clause in the Guardian’s house agreement that he had himself negotiated some years earlier (it was intended to help save money during one of the paper’s financial crises), he was able to persuade Viner to agree to him taking “unpaid leave of absence” while remaining on the staff. Her decision was widely criticised among Guardian staff. Milne has now become part of the Corbyn story; some members of the political team feel inhibited from writing about a colleague and fear that Milne may complain about them to Viner.

In his new job, Milne has little direct contact with lobby journalists; except on big issues, they are briefed by Kevin Slocombe, a former trade union head of communications. Milne’s responsibilities are to develop a strategy for media relations and to oversee focus groups and private polling. He brings his deep knowledge of the labour movement. As a former chair of Hammersmith Labour Party in west London, Milne organised an election campaign for the then local MP, Clive (now Lord) Soley, and attended annual conferences as a delegate. His biggest weakness, as most lobby journalists see it, is that he is even less flexible in his views than Corbyn.

“His instincts are to be unwavering on every issue,” said one. “He is more Corbynista than Corbyn. He pressed for a three-line whip on Syria and a shadow cabinet that more closely reflected Corbyn’s views. On the day Labour was launching its EU referendum campaign, Corbyn went to speak at an anti-Trident rally. A good spin doctor would have advised him not to go. Seumas actually went with him.”

Another source, close to the leader’s office, criticised Milne for not shutting down repeated allegations that Corbyn and other leading figures in Labour are too soft on, and even sympathetic to, anti-Semitism. “Milne encourages Jeremy to parade his values, saying he’s against prejudice of all kinds, rather than straightforwardly denouncing anti-Semitism.” The same source said: “Milne puts ideology above good management of the team. That is why there have been so many rows.”

Nevertheless, after an understandably slow start, there are signs that he has begun to knock the Corbyn operation into more professional shape. As a tidy dresser – fashionable and youthful-looking, he abandoned Mao jackets for suits some years ago – he understands that radicals should not detract from their message by dressing sloppily. He has therefore introduced what lobby journalists call “Project Suit” for Corbyn, so far getting him into a matching jacket and trousers. He is also trying to educate him in the elementary political skill of saying what he wants to say during interviews, rather than answering every question literally. He wants to refine the Corbyn message into two or three flagship policies. These are unlikely, I am told, to include anything on defence or foreign affairs, areas on which Labour is most divided internally. Milne, contrary to some reports, is not personally very exercised over Trident, but he recognises that it is hard for Corbyn to drop or even downplay the issue, because it was so central to his campaign. Nor is Milne, again contrary to reports, at all keen on mandatory reselection of MPs, with its echoes of the 1980s.

***

In recent weeks, the Corbyn team has become more proactive in setting the political agenda, demanding an inquiry into the offshore funds owned by David Cameron’s father and a reversal of cuts in capital gains tax, even if it has been too eager to call for senior ministerial resignations whenever there is a period of difficulty for the Tories. On economics in particular, it has begun to offer a more coherent critique of the government’s strategy: more confident, in some ways, than what Ed Miliband offered, as one of the former leader’s aides admitted to me.

Some of this is attributed to Milne. A few lobby journalists who remember the ranting, expletive-strewn style of former Labour spin doctors such as Tom Baldwin have begun to warm to his calm, reserved manner. Yet even those who like Milne suggest that his experience of the media is too limited. “He doesn’t understand the rhythms of news,” one reporter told me. “He doesn’t understand what Sunday newspapers want or what the main broadcasting channels want. He doesn’t even engage with the BBC properly.”

When Milne took up the job last October, his more sceptical colleagues at the Guardian predicted he would be back in the office by Christmas. It is perhaps more realistic to expect him back before next Christmas. Rumours of a summer coup by Labour MPs against Corbyn persist and, even if his successor is also on the Labour left, he or she is unlikely to retain so controversial a figure. It is not impossible that sacrificing Milne could be a price that Corbyn has to pay to remain as leader.

Seumas Milne would probably not protest all that much. He has been heard to complain of tiredness and getting too few days off. He is bemused by the way falsehoods and distortions circulate at Westminster and into the media without ever being properly denied. He hates the intrusion into what he regards as his private life.

As he contemplates a constantly feuding Labour Party, a return to his filing cabinets and overburdened desk at the Guardian and to the company of reliable, ideologically sound comrades inside and outside the paper must look increasingly attractive. But in his own view, he will have done his duty to try to advance the socialist cause, as he has done, so often unavailingly, for more than four decades.