In the end, even pornography can become a form of nostalgia, I suppose.

It's the late 1970s. I'm a teenager and I'm sneaking into my dad's room to "borrow" the men's magazines his former army buddies keep bringing him. Mayfair, Whitehouse, Men Only. Names that reek of that time just as much as Embassy Regal, Angel Delight or Denis Healey. I'm looking for some illicit glimpse of the adult world in their pages. And though I don't know it in my bedroom right on the edge of the UK, in a small way I'm playing a part in a revolution in British society. A revolution whose Che Guevara is a man with candyfloss hair and a fur coat, who speaks in a version of received pronunciation that has clearly been tortured in a dark room (how else could it sound so strangulated?) and a man who made his money from nudity yet who saw himself as a class above your common-or-garden pornographer.

Fast-forward nearly 40 years. It is March 2013 and I'm in Soho, the "square mile of vice" as the tabloids used to call it, in search of one of its most famous – or maybe that should read notorious – inhabitants, Paul Raymond. The man behind Men Only and a whole host of other skin trades.

Raymond, for a time Britain's richest man, died five years ago and now his gilded, gutter life has been made into a movie. The Look Of Love stars Steve Coogan as the owner of the Raymond Revuebar, property magnate and porn baron, while Tamsin Egerton plays model, actress and Men Only columnist Fiona Richmond (a name that could make any 1970s teenager's knees tremble). No doubt Raymond would have loved it. It's great publicity, and he always knew the worth of publicity.

Michael Winterbottom's film renders Raymond's life – and the story of the "permissive society" that it encompassed – as a form of jaded, slightly sour comedy (before taking a handbrake turn into tragedy near the end). Between the cracks though, there might be a more interesting story to be told. A story that is part geography, part social history, part sexual history. And it starts in Leicester Square.

Paul Willetts and I are standing outside the Empire Cinema, discussing the history of striptease in the UK. In 1847 a "palace of varieties" was opened on this site. The main entertainment was Madame Walton's Pose Plastique and Tableau Vivant. Or nude and nearly nude models standing still. "There were nude shows as early as that," explains Willetts. "They were given this cultural gloss by mimicking famous paintings."

For all that Philip Larkin claimed that sexual intercourse began in 1963 (between the end of the Chatterley ban and the Beatles' first LP), nudie shows have a much longer history in the UK than is often thought, Willetts explains. As Raymond's biographer and Soho historian (even though he lives in Norwich these days), Willetts is the perfect guide to London's seedy, sinful history (to go all News Of The World on you for a moment). He can tell you the history of the Windmill Theatre, which claimed to have invented the 'living tableaux' in the 1930s (it was against the law for them to actually move), and point out to you the site of the rather anonymous building in Irving Street that was home to Britain's first strip club in 1957 (a year before the Revuebar opened), a club that counted among its patrons Kingsley Amis and a certain Philip Larkin. Raymond too.

"He saw stuff at the Irving and he thought 'actually I can do this better'," says Willetts.

Raymond's early back story takes place in Britain's post-war variety halls. Born in Liverpool in 1925, he trod the boards with a "mind-reading act". But he soon realised he was better behind the curtain. As Willetts suggests in his biography, the one true act of mind-reading that you can attribute to Raymond is that he read theatre patrons' minds. And in those minds he discerned that sex sells. By the start of the 1950s he introduced a new act, "Nudes In The Night", into the variety tours he was organising. Surprise, surprise, ticket sales picked up dramatically. Soon he was sending shows around the country entitled Folies Parisienne and Nudes On Ice (think of the goosebumps). When one turned up in the Glasgow Empire, Raymond's nudes were pelted with beer bottles.

The opening of the Revuebar was the real key to his success – and his reputation. And straightaway there was an element of snobbery on display. "He was aspiring to create something like the Folie Bergere," says Willetts. "It was quite cabaret and much more stylish and wholesome, dare I say it."

It made sense to open it in London's Soho area. In the 1950s it was reaching the end of its days as the city's Latin Quarter, where General De Gaulle had hung out during the war, drinking in the French House where Raymond would later drink too. "Soho was this little island of olive oil, which you couldn't buy anywhere but a chemist's shop. So it had this genuine otherness about it."

The Revuebar was an immediate success. "It did tremendously well," Willetts points out. "It tapped into all sorts of traditions really." Including a kind of internationalising of sex itself. "The Raymond shows always had these titles like Night In Paree, Ooh La La and then, by the 1960s and 1970s, it was Swedish Girls Go On Holiday. There's this odd way we sort of latch onto some nationalities and sexualise them." Indeed. Others – English, Irish, Welsh or Scots remained inviolable. You'd never have seen "Highland Heat" or "Unstitch That, Jimmy".

We wander up to Brewer Street to stand in front of Maurice House, the site of the Revuebar. On the wall you can still see the neon sign that once shone out into the London night. It's an unloved thing. The paint is peeling. To the left you can see the enclosed bridge, now rather grubby and water-stained, across which in Raymond's day a white horse was regularly led into the theatre space where it would then remove the clothes from a stripper (the things you can do with the help of sugar lumps).

The building is still a club, called The Box, a theatre of varieties according to its website, a "fetish burlesque" nightspot, according to the Evening Standard, frequented by various Harrys (Prince and Styles). We are given a quick show round by one of the events team who tells me her name is Gigi Playfair (I so want that to be true). On the stage a dancer and a dwarf are practising lifts. For The Look Of Love, the filmmakers "built" a Revuebar and Willetts spent a day there watching filming. "It was like some speeded-up film. It went from 50s chic in the morning to tatty 80s with an Alexei Sayle-style comedian."

Over that time you could argue that Raymond had played his part in transforming the country, through his skin magazines and some of the worst films ever made in Britain – the likes of Frankly Fiona and Let's Get Laid – have as yet to be subjects of a retrospective at the Edinburgh International Film Festival. But they had an impact. "He sold an idea to the provinces. If you were coming down to see Scotland play England, you'd say 'we're going to Wembley but before that we'll go to Soho'. His publishing company pushed that out to every high street."

To do so he fought legal battles, had his publications regularly seized and debated in favour for the permissive society. (Willetts appears in the film as Lord Longford: "I had this really weird day with Coogan flourishing hardcore pornography in front of me.")

The entrance to the club is in Walker's Court, one of the few streets in Soho that still pulses with the language of seedy Soho. "Adult", "Peepshow", "Private Dancing". This is, in one sense, Raymond's legacy. Not much of one, is it? But to be fair to him, he was an equal opportunities skin merchant. He was one of the first to present gay-orientated shows in Soho, at a time when homosexuality was still illegal. Which is a form of bravery. And in doing so he played a part in the more liberal attitudes we hold about sexuality now.

Of course, for Raymond it was the pink pound and not the pink politics that caught his eye. Towards the end of the film version of Raymond's life, the story dissolves into one drug-fuelled orgy scene after another. And yet, to Raymond, "it was money not sex that mattered," as Willetts points out. "He was full of paradoxes. He made a fortune out of making the private public. He was inhibited in lots of ways and he had this rather camp, theatrical style. He was also rampantly heterosexual. He was an odd guy. Tremendously mean in some ways. And kind in others."

Paul Raymond died at the age of 82, having helped transform our notions of sexuality, for good and ill (the film makes no judgments). We now live in a world of lap dancing clubs and internet porn. A world where gay bars and clubs can be found in every city. To some extent, we all live in Soho now.

The Look Of Love is released in cinemas on April 26. Paul Willetts's biography The Look Of Love is published by Serpent's Tail, priced £8.99.