John McDonnell likes to recount a bittersweet story about visiting an office in his own West London backyard during a dispute over its future. “I’m going down there to tell management they’re not going to have their way with these workers, we’re going to protect their jobs, and if anything happens, we want guarantees against redundancies.”

The office housed the service records of British military personnel. McDonnell mentioned to the union rep that his father, Bob, had been a sergeant, serving in the Sherwood Foresters on what the Labour shadow chancellor calls “mopping up operations” towards the end of the Second World War. “So I go and meet the management and then halfway through, they come in and just pass me a file. It’s my dad’s old Army file, one of those browning paper folders.”

McDonnell is proud that his father, a Liverpudlian docker, served his country and was delighted that the staff took the time to dig out the file. “Everything was in,” continues McDonnell, “and the final remarks from a commanding officer were ‘he’s a smart soldier’ and ‘I would commend him to you’ and all that stuff.” Also buried inside was a note that McDonnell senior had been fined half a crown for damaging his motorbike. “Unfortunately my dad was dead by this time. I’d have loved to take it up with him.”

The sweetness of the tale lies in McDonnell’s pleasure in this snippet of family history and the consideration shown by the civil servants. The bitterness lies in what happened to the office next: “Bloody New Labour privatised the place.”

“Hello,” McDonnell recently greeted a businessman, “are you looking forward to having a Marxist in No 11?” You never know how seriously to take these kind of lines from McDonnell, but he certainly has a very Marxian interest in who owns the means of production. In early September, he made a splash with a radical scheme that would require companies to earmark part of their profits to purchase a chunk of their own shares for their workforce.

It is hard to imagine any of his recent predecessors coming up with that. Indeed, as the first Marxist sympathiser to hold the Treasury brief since Stafford Cripps did the job in Attlee’s post-war government, McDonnell is perhaps the most intriguing figure in Jeremy Corbyn’s party, which—despite everything—is tantalisingly close to power.

An outsider in Labour’s Blair-Brown years, his influence in the Corbyn era goes beyond his economic portfolio. And he has been busy not only battling the Conservatives, but also fighting to shift the centre of gravity in his party. He embraces Marxism as being, as he put it at a 200th birthday celebration for Old Whiskers this year, a “force for change today.” This enthusiasm goes right back—as a TUC apparatchik, he chaired a weekly book group on Das Kapital—and continues. On the eve of Theresa May’s big Tory conference speech this autumn, he will become vice president of the Marx Memorial Library in central London.

When asked in 2006 to name his most significant influences he said: “Marx, Lenin and Trotsky, basically.” His new leadership role might have moderated him. He now also cites the left-wing American Keynesian Joseph Stiglitz and namechecks the late Marxian proselytiser Ernest Mandel, the radical finance expert Ann Pettifor, and Graham Turner, a consultant probably best known for recommending part of the Bank of England be transferred to Birmingham.

Practical moderation—or pragmatism—has been one of the most fascinating aspects of McDonnell’s reinvention. Colleagues speak uncomfortably of the hardliner they’ve known for decades developing a chortle, half smile and shoulder shrug for the television cameras, which he uses when deflecting criticism. The responsibility of a frontline role has resulted in a velvet glove cushioning the iron fist.

On The Andrew Marr Show in September, he thanked the former chief rabbi, Jonathan Sacks, for being “brutally” honest in comparing Corbyn to Enoch Powell, before arguing that Sacks was wrong. He sounded sorry to see Frank Field go. The socially conservative pro-Brexit MP who claimed he quit the Labour whip over anti-Semitism was suddenly, McDonnell said, “an old mate of mine.”

Has avuncular charm been used to ulterior ends? Enemies suspect as much, and mutter that he has a bright brain and dark heart. He is, undoubtedly and at once, both down to Earth and dogmatic. One dimensional he isn’t.

Rise of a Stakhanovite

McDonnell and his then wife moved to London in the 1970s. It was a decade before he came to prominence at the Greater London Council (GLC) during the rate capping confrontation, and then the doomed struggle against Margaret Thatcher’s partisan move to abolish the authority. The young couple took jobs as house parents in a children’s care home.

They were responsible for raising 10 children. “Most had been taken into care, largely because of mental health issues for the parents and some cases of child abuse. We tried to give them stability, like a family. I’d take them to see my mam.”

At the same time, McDonnell studied for an economic history, politics and government degree at Brunel University, followed by a masters at Birkbeck College. “I was an hour late for an exam because one of them had run away,” he says. McDonnell and his wife had two daughters before their marriage ended in 1985; he also has a son with his second wife Cynthia Pinto, who is of Goan descent.

Nobody could seriously accuse McDonnell of lacking experience of life before politics became his life. He was born in Liverpool in 1951 to Bob and Elsie, a cleaner. They lived in a rundown block off Scotland Road. He’s too self-aware to indulge in lurid Pythonesque descriptions about having grown up in a shoe box. Instead, he just says: “Some of the sociological studies say they were some of the worst slums in Europe, and we used to just call it home.”

Dock work dried up so the family moved to Elsie’s hometown of Great Yarmouth in Norfolk, where she worked behind the biscuit counter in the department store BHS (this added fuel to his fury when Philip Green sold the chain). Bob became a union activist bus driver.

McDonnell and his brother, who became a police chief superintendent, went to the local grammar. After a year he was sent on a church grant to De La Salle College in Ipswich, a Catholic boarding school, to prepare him for the priesthood. “We were the classic Irish Catholic family, which meant one of us was going to be the priest,” he says with a sigh.

The altar boy who had to get up early every morning for Mass didn’t enjoy the experience and doesn’t talk publicly about it, but others have heard him speak of De La Salle in terms of “sado-masochistic Christianity,” a regime that enjoyed “kicking the shit out of you.” McDonnell sticks to: “I did a few years there until I was 15, 16 and basically discovered girlfriends, so celibacy wasn’t going to be an option. I was also into politics.”

No longer religious, he’s happy to be described as a “cultural Catholic” and is a regular visitor to the church near his Hayes home. “I miss the ritual of it, I miss the old Latin Mass. It was a good grounding,” he says. “The local parish priest optimistically describes me as a lapsed Catholic. I go to the Catholic church for a lot of funerals and celebrations and stuff like that.” Does he recite prayers and sing hymns? “You can’t help yourself. The smell of incense and you’re away.”

McDonnell’s journey from Catholicism to Marxism didn’t jar for a thinker who identifies an overlap between the two. “Catholics have always been at the heart of the labour movement,” he stresses, “and fighting for justice and equality. Just look at the worker priests. Pope John XXIII had a big influence on me in the 1960s.”

Pope John is revered by Catholic progressives for his views on equality and for saving Jews during the Holocaust, yet it’s a jolt to hear that he’s a poster boy for the shadow chancellor alongside Marx. There’s a touch of the Old Testament prophet in McDonnell when he preaches his religion of socialism, insisting the meek are entitled to inherit the world—with the fat cat heirs to the money changers booted out of corporate temples.

At grammar school he flunked his A levels, partly due to having jobs in bars and a bingo hall (he remembers the call “Wilson’s Den, No 10,”) and went to work in a Birds Eye hamburger-and-peas plant. Returning to Northwest England to graft in a Silentnight bed factory, and then a Philips television plant while redoing A levels at Burnley Tech, taught him hard lessons that make late sittings in the Commons a doddle. “I never forget 3am when you’re on a night shift and you’ve got another three hours to go. ”

Even Tom Watson, Labour’s more mainstream deputy leader who has often clashed with McDonnell, is in awe of how hard he pushes himself. “John’s the hardest working member of the shadow cabinet, with a Stakhanovite work ethic,” Watson says. “He’s also one of the cleverest men I’ve ever met. If he’d ever chosen a career in business he would’ve been a brilliant commercial strategist.”

Corbyn’s complement

Instead, he chose a career in politics, one that got going with his finance role at the GLC—or “chancellor of the exchequer for London,” as McDonnell half-jokingly puts it. He challenges accounts painting him as the most uncompromising hardliner in those divided times. But he admits things were “all pretty gory” in his falling out with the GLC’s leader, Ken Livingstone.

They were playing a game of chicken with the Thatcher government by refusing to set a rate. While McDonnell refuses to be styled as the ideological fanatic in that battle, he criticises Livingstone for failing to stand firm. Whatever happened, that rift never fully healed.

What’s remained solid is his friendship with Corbyn. McDonnell first stood in the Hayes and Harlington constituency in 1992, losing to Tory right-winger Terry Dicks by 54 votes. Elected to parliament in 1997 in Labour’s landslide, he almost immediately formed an alliance with a comrade who already had 14 years’ experience in the place.

“Jeremy and I complement each other. He’s a really nice guy, he doesn’t want conflict but don’t underestimate the bit of steel he’s got in him as well,” says McDonnell. “Sometimes it’s me that’s had to be frank with people. I have a bit of a reputation for being a bureaucrat but you need that.” It probably helped that Corbyn focused on foreign affairs, particularly anti-colonial movements, while McDonnell concentrated on domestic issues including work, trade unions and social security.

The pair were at the heart of what McDonnell, then chair of the Socialist Campaign Group of MPs, describes as “effectively the left opposition on the backbenches,” during the Blair-Brown period as they confronted their party leadership on policies from PFI to Iraq.

Both supported a united Ireland and associations with Republicans caught up with them after Corbyn became Labour leader. McDonnell had claimed that the “bombs and bullets” and “bravery” of the IRA had led to the Good Friday Agreement. His words were, characteristically, more direct and so—potentially—much more dangerous than Corbyn’s controversial remarks about Zionists, with no room for textual analysis about whether they were going to cause offence.

But McDonnell, unlike Corbyn, proved adept at closing the argument down and moving on when the controversy surfaced: he quickly apologised “from the bottom of my heart.” Early this summer during a party awayday, he was involved in a top floor shouting match with Corbyn’s team as he urged a line be drawn under the damaging row by adopting the more contested examples of anti-Semitism in the now totemic international definition. After weeks of needlessly negative headlines, he prevailed in September.

McDonnell’s is the shorter temper. In 2009, the Labour government decided to bulldoze homes in his constituency to make way for Heathrow Airport’s third runway. When the plans were being unveiled in a statement to the Commons, he grabbed the ceremonial mace in protest, earning a week-long suspension

Twice he tried to run for Labour leader, and twice he couldn’t get sufficient support from MPs. In 2007, he failed even though no other candidate stood in the way of Gordon Brown, who went on to be crowned without a contest. In 2010, he was bent on having another go, unconvinced that Diane Abbott was the right socialist candidate to challenge New Labour.

But when it looked like neither of them would get enough nominations, he stood aside to let an unmistakably left-wing voice be heard in a leadership contest for the first time since the 1980s. “She did alright,” says McDonnell. The lack of enthusiasm indicates the frostiness between the pair. When it emerged that she was sending her son to an expensive private school, McDonnell asked her to quit as a Socialist Campaign Group officer. She refused.

In 2015, McDonnell was pivotal in Corbyn’s takeover. Initially urging Ed Miliband to stay on after his defeat, McDonnell admits he thought his wing of the party had no chance. The key moment was persuading Corbyn-sceptical MPs to put him on the ballot to widen the debate. Shock and rage at that year’s unexpected Tory majority and hope for an alternative propelled Corbyn to a sensational victory. It was so unexpected that during the campaign, McDonnell was teasing friends that MI5 would shoot Corbyn if he got anywhere near power.

There was an abortive attempt to keep McDonnell away from the Treasury brief in the first round of appointments: “Unions lobbied for me not to be shadow chancellor. They wanted Owen Smith—Len included.” The Len is McCluskey, Unite’s general secretary. They’ve since made up but it clearly still rankles.

McDonnell served as Corbyn’s praetorian guard during the 2016 abortive post-referendum coup as shadow cabinet members quit in droves and MPs signed a no confidence motion. Some frontbenchers claim they then saw the old “real John”—abrasive, unpleasant, hostile, uncompromising, dogmatic—rather than the more measured, television-friendly version. As the contest got going, at a pro-Corbyn rally he dismissed the plotters as “fucking useless,” and although he soon brushed these words aside as stand-up comedy, to some it looked like a flash of the old steel.

In the end, the crisis cemented him as Corbyn’s effective deputy and he stamped his authority on the Labour 2017 election manifesto, which promised to renationalise water, gas, electricity, mail and rail. It also proposed to raise an extra £19.4bn from corporation tax, a vast bill which some have suggested that business would find ways to wriggle out of paying.

But all this money was earmarked for crowd-pleasing purposes, including the health service, cancelling a few brutal benefit cuts and—most eye-catchingly—the abolition of student fees. There were also ideas about encouraging public and other forms of investment to bolster the economy, but this was a very political manifesto, with the stress on the tangible benefits of ending austerity rather than any McDonnellite theory of economics.

To bulletproof the proposals, McDonnell had a team of number crunchers locked in a room for days producing tables detailing how extra public expenditure would be funded. The Institute for Fiscal Studies cast doubt on many of the calculations, but it contrasted well with the arithmetic-free Conservative manifesto.

Unlike Gordon Brown or Ed Balls, this Labour Shadow Chancellor boasts about tax rises on the richest and makes no attempt to camouflage increases. Nor is he as interested as Balls was in getting into arguments about how far it makes economic sense to borrow now and pay for things down the road. He buys the basic Keynesian insight about borrowing to invest, but doesn’t list Keynes himself, that great liberal, as one of his intellectual heroes. He sees no need to pretend his plans will make every last business better off, because he takes a class war pleasure in corporate squeals of pain, as well as raids on the richest 5 per cent of individuals.

Although his specific plans for the latter are not so severe, his tough talk could pave the way for radical moves if he eventually makes it to No 11: government actions rarely stop with just the pledges in the manifesto.

Applause from the TUC is contrasted by unease from a corporate world desperate to woo a potential Chancellor. Bosses complain to Iain Anderson, executive chair of the Cicero Group (lobbyists working with companies in the financial, energy and infrastructure sectors) that the shadow chancellor is elusive.

“Business is keen to see a lot more detail from McDonnell. He comes across as the amiable bank manager in a suit, but there are real concerns about his economic prospectus ripping up property and ownership contractual rights,” says Anderson. “He says he wants to work with business but… It doesn’t look like [he is serious about] it yet.”

A Labour-friendly business adviser, who is a long-term member of the party and minor donor, is more scathing. “Companies think he’s a Marxist revolutionary who will wreck the economy,” he seethes. Captains of industry may have picked up on one personal detail of his: the notorious—and jocular?—hobby he lists in Who’s Who: “generally fomenting the overthrow of capitalism.”

The bosses are, this donor continues, “emotionally terrified about him becoming chancellor but don’t really believe it will happen so in practice they’re not that bothered.” But, should it happen, they will soon worry about “taxes going up but also their salaries and bonuses being hit.”

Even if he’s not sharing much of his thinking with business, he’s working on Labour’s next manifesto with Bob Kerslake, a crossbench peer and a former head of the Home Civil Service, who takes ex-civil servants and think tankers to meet him and prepare an opposition for the possibility of high office.

“Each policy has to be tested to destruction,” says McDonnell. “We will be credible. We know we’ll be held up to scrutiny, by the media—greater scrutiny than the Conservatives. So we need to be ready.”

Another pressing reason to be ready is the possibility of a Brexit uncivil war collapsing an unsteady Conservative government, triggering a general election long before 2022. McDonnell’s hedging his bets. “I had been saying pessimistically they would cling on to the end, that’s what Tories do. Now I think anything can happen so the pace of preparation must speed up.” The urgency he feels about taking power is sincere and palpable, although he concedes that the Conservatives holding on is more likely.

Like Corbyn, his Bennite background fosters a certain suspicion towards Europe and he might in theory welcome being free of EU state aid rules, which restrict industrial policy. But he’s serious about wanting to be chancellor, and he doesn’t want to be devoured by the Brexit crisis that could yet consume a lot of people, perhaps whole parties: he senses a way out could come in handy. More pointedly than Corbyn, and shadow cabinet colleagues, he has left open the option of backing another referendum as the number of trade unions and local Labour parties asking for a people’s vote climbs.

JM4PM

Corbyn will not last forever. There have been moments this year—as early last, and the summer before that—where even some of his sympathisers have looked at him and wondered whether he is right for the role. Should Labour lose a second successive election, he would almost certainly step down: the left would require a candidate.

Publicly, McDonnell has pushed Rebecca Long-Bailey, a 2015 Salford MP with the business brief. But shadow cabinet members privately speculate on whether McDonnell would throw his own hat in the ring. Sitting opposite Corbyn, one regular attendee at shadow cabinet meetings sees an “it should have been me” expression on McDonnell’s face when the leader digs himself into a hole.

“If Jeremy fell under the proverbial bus,” says that shadow cabinet member, “I’ve no doubt, absolutely no doubt, that John would look closely at the situation and consider all the options, then conclude the successor should be a man of his age born in Liverpool who now represents a constituency in West London. You or he will never convince me he doesn’t want to be leader until John McDonnell’s left parliament and is out of politics. I’m not sure I’d believe it even then.”

McDonnell’s charm offensive will do him no harm, though it might do him no good with parliamentary colleagues who clashed in the past with a tough operator. His insistence “you can’t hold grudges in politics” and his tactic of “kill them with kindness” raises eyebrows with Labour MPs who remember bruising encounters.

In private as well as public, the driving force behind Corbynism denies he’s interested in the top job. His health will always be an issue, and the varied terms in which he describes his 2013 heart attack—at times he has called it “major,” at others he has stressed that only one stent was required—could be a sign of how his private ambitions wax and wane.

But the refusal of so many in Labour, friendly to him or not, to accept McDonnell’s denials is a tribute to his importance in the left’s project to transform Labour. And if not him, who? For now though, McDonnell is focused on becoming chancellor, a job he wants because he believes he can make a difference for the poorest and most vulnerable in society. He has, he insists, not forgotten his roots.

On the return of MPs from summer recess, about 50 people marched to parliament demanding a living wage for cleaners in the Ministry of Justice. A woman with a microphone chanted: “You fucking shits, you hypocrites, Ministry of Justice my arse.” And who was at the front of this demo? None other than John McDonnell. The agitator who spent his life protesting—and who could soon be in a position to order the department to pay fair.