When I worked at the Daily Mail, I began to think of it like Willy Wonka’s chocolate factory. It wasn’t exactly that “nobody ever goes in and nobody ever comes out” – after all, there was a steady stream of workers on the escalators up to the airy atrium above Whole Foods in Kensington, west London – but the whole operation felt so hermetic.

Outsiders saw it as a strange citadel, where political reputations were created and destroyed, and where our national conversation was greatly enlivened or maliciously poisoned (depending on your point of view). But its workings were hardly ever exposed to outside scrutiny, even by the cloistered standards of the press. Every day, the Daily Mail casts its eye over the world, and usually finds it wanting; the world hardly ever gets to gaze back.

As with so many elements of the Mail, this secrecy springs directly from its editor’s psyche. That is why, when news broke that Paul Dacre was stepping down after 26 years, so many commentators hailed it as the end of an era.

The Daily Mail is the most influential newspaper in Britain, and its editor has the purest power of any person in Britain. His successor, the Mail on Sunday’s Geordie Greig, has a close relationship with the group’s proprietor Lord Rothermere, but it is inconceivable that he will preside over a paper that reflects so precisely his own enthusiasms, hang-ups, obsessions, and vendettas. Dacre was Fleet Street’s last silverback gorilla.

Outsiders tend to imagine him as a Malcolm Tucker-style ranter, an aggressive whirlwind of effortless expletives. Yet over five years of working at the paper, as a sub-editor and then on the features desk, I discovered that he was more complicated than that. At heart, Dacre is a shy man, uneasy in company – the opposite of a raconteur. He is well north of six feet tall, yet walks with his head dropped as if aware that he takes up more space than other people. The sound I most associate with him is not a scream, but a low growl. There was always the sense he had to work himself up to his nightly denunciations of his luckless executives.

You can see that tension between reserve and anger in the newspaper, which presents itself as the champion of the little guy – of quiet, suburban homeowners living defiantly ordinary lives, whose values are defined by their exclusion from a glittering, liberal, cosmopolitan elite.

They are exercised by leylandii disputes and microscopic incursions on their boundary walls (I swear I subbed a piece on these subjects every other month; the same neighbours were sometimes at war for years). They are deeply moved by the plight of captive orangutans, dancing bears and neglected dogs. They are happy to read the same story about the BBC running too many repeats at Christmas every winter. They devour the effortlessly horrifying health section, where a sub once fainted while editing a particularly gory piece on testicular torsion, and which gave rise to my favourite ever Mail headline: “Surgeons made me a new tongue from a piece of my arm.” (Yes, it was still a bit hairy. Yes, it’s been a decade and I’m still not over it.) They are apparently happy that Richard Littlejohn’s column is less a piece of prose and more a recital of in-jokes older than their children: mind how you go, you couldn’t make it up, here we go Looby Loo.

We used to joke that every Saturday essay – the paper’s prime commentary on the state of the nation – could be headlined “The Great Betrayal”. Every obituary of an artist or author essentially boiled down to one question: “Genius or Pervert?” (They were often both.)

These are not the bits of the paper that reach people who don’t buy it. To many of them, the Mail is defined by its excesses – the appalling front page describing judges as “enemies of the people”; the description of Mick Philpott, who killed six of his 17 children, as a “vile product of Welfare UK”; the attack on Ed Miliband’s late father Ralph, a Jewish refugee who volunteered in the Navy, as a man who “hated Britain”.

Any attempt to show that there is more to the Mail than vicious right-wing polemic will inevitably be seen as apologism for that polemic. But appreciating the craft of the print product is vital to understanding why nearly 1.4 million people read it every day, as is the statistic that 15 per cent of them voted Labour in 2017. People might have been lying when they claimed to “read Playboy for the articles”, but some really do read the Mail for the leylandii disputes.

For that reason, it is unsurprising that sources at the paper have been briefing that Greig will “detoxify” it – I’m not sure there is a commercial incentive for the nastiness. A less powerful editor might even have been told to rein it in before now, for fear of spooking advertisers in a troubled market.

Dacre hates public speaking, and he has left a meagre trail for any outsider trying to understand him. Unlike Rupert Murdoch’s editors, who are strongly discouraged from putting themselves forward, there is no corporate pressure to stay in the background. It is Dacre’s personal choice.

One of the few clues to his psychology comes from a BBC Desert Island Discs appearance in 2004, where his luxury was the Guardian, because “its patronising, right-on, sanctimonious political correctness gets me so angry it would give me the energy and the willpower to get off that island”. That was an enormously telling answer: just as liberals love to hate the Mail, so the Mail’s editor loves to hate liberals. Both derive a sense of purpose and energy for campaigning from their outrage at a caricature of their opponent. They need each other, somehow, and the resulting friction feeds the engine of British public life.

The immense angst generated by the Mail is also fascinating because it reveals one of the biggest drivers of modern politics: the contest for victim status. Liberals point to the Mail’s treatment of immigrants, welfare claimants, famous women who’ve got a bit porky and footballers who dare to enjoy their money, and see a bully. They do not understand how someone who earns almost £2.5m a year, spends a month at a time on the British Virgin Islands, owns a fishing estate in the Scottish Highlands and a house in West Sussex, and edits the loudest and angriest of Britain’s newspapers, can see himself as an underdog. But Dacre does.

Born in 1948 in Enfield, north London, he attended the private University College School on a scholarship and then Leeds University. His father, Peter, worked his entire career for the Sunday Express. Dacre joined the Daily Express in Manchester on graduation, later saying in one of his rare interviews: “There was never any desire to do anything other than journalism.” His wife is a drama lecturer; his son James runs a theatre.

In his world view, the decent people of Britain are silenced and denigrated by an elite that includes, but is not limited to, judges, the House of Lords, “fat cat bankers”, jobsworth council employees, the European Union and the BBC. Under his editorship, the Mail’s political views were not as predictable as you might expect. It flirted with Ukip but the relationship remained unconsummated.

It always surprises me that the Mail backed Ken Clarke over Iain Duncan Smith in the 2001 Conservative leadership contest. “Is it better to belong to a small right-wing faction that is characterised by the purity of its opposition to Europe but faces years in the wilderness?” the paper asked. “Or is it preferable to oppose the single currency as part of a diverse party that can provide robust and desperately needed opposition to Mr Blair’s elected dictatorship on a range of issues and could form a credible government?”

Inevitably, Dacre hated Tony Blair for his flashiness; he liked Gordon Brown for his moral solemnity and has always admired Theresa May precisely because she lacks charisma. To him, eloquence is suspicious, a way to bamboozle people with charm; dowdiness is a mark of seriousness. I remember working on the subs’ desk the evening that James Purnell resigned from the Labour cabinet, in a direct challenge to Brown. The night desk were all set to change the splash – a move that would have increased the prime minister’s jeopardy – until, quite suddenly, they weren’t. A particularly grisly murder therefore stayed in place, as did Brown.

This makes Dacre’s departure in November a sad day for May. It will also be a profoundly disconcerting experience for the Mail’s senior executives, who tended to react to his reign of terror in one of three ways. A small number maintained their equanimity, even finding the outbursts morbidly entertaining; a second group grimly kept their heads down until they suffered a breakdown. The final group succumbed to a kind of Stockholm syndrome, reasoning that if they had been called a “cunt” so many times, perhaps that was because they were one? I expect this group will have the same trouble adjusting to post-Dacre life as long-serving prisoners do to day release, overwhelmed by the possibility of choosing their own lunch. Perhaps they can hire someone to shout at them.

Yes, make no mistake: the man is terrifying, and has been known to send sorrowful messages, via proxies, to those who criticise him. Without him, the paper will be deprived of its restless, endlessly unsatisfied animating spirit – and possibly some of its lavish resources.

Paul Dacre is the Daily Mail, and the Daily Mail is Paul Dacre. Then again, maybe the readers won’t notice as Remain supporters or social liberals begin to creep into the pages – as long as they still have the leylandii.