From today, you can pop into The Bookshop, a new period drama adaptation of the Penelope Fitzgerald novel. While you are browsing, you can get to know a courageous widow (Emily Mortimer), a melancholy recluse (Bill Nighy) and a snobbish busybody (Patricia Clarkson), all of whom live in a coastal town in 1959. The only snag is that you may feel as if you have visited this particular shop already. You may get a frisson of deja vu from the china teacups and the crystal champagne glasses; the ankle-length skirts and the three-piece suits; the cobbled streets and the unspoilt woods; and all the other signs that the UK film industry’s latest obsession is Britain as it was a few decades ago.

British films have always idealised our great nation’s glorious past, of course, especially when that past is embodied by Henry VIII, Queen Victoria, Mr Darcy, or Helena Bonham Carter wearing a bustle, but never before have so many films, released over such a short time, targeted such a specific period of our history: the outer rings are the 1920s to the 1960s, and the 1940s are the bullseye.

Since the beginning of 2017, there have been three films concerning the Dunkirk evacuation: Christopher Nolan’s Dunkirk, Joe Wright’s Darkest Hour and Lone Scherfig’s Their Finest. Goodbye Christopher Robin opens during the second world war, before flashing back to the creation of Winnie-the-Pooh and its effects on AA Milne’s family in the 20s and 30s. (A Disney film with Ewan McGregor as a grown-up Christopher Robin is due out in August.) The Guernsey Literary and Potato Peel Pie Society opens in 1946, and the narrative then cuts back and forth between the island’s Nazi-occupied war years and their immediate aftermath. Lenny Abrahamson’s The Little Stranger, which is released in the UK in September, is set in 1947. Andy Serkis’s Breathe begins with a friendly game of tennis at the British embassy in Nairobi in 1958. On Chesil Beach, based on Ian McEwan’s Booker-nominated novella, is mostly set in 1962 (with flashbacks); and The Mercy, starring Colin Firth and Rachel Weisz, brings us bang up to date: it is set in 1968.

If I broaden the field to include recent British films that don’t take place in Britain, there is Gurinder Chadha’s Viceroy’s House, set in 1947, Armando Iannucci’s The Death of Stalin, set in 1953, and Pawel Pawlikowski’s Film4-backed Cold War, the only vaguely British film in competition at Cannes this year, which starts in 1949 and spans the 50s. And if I broaden the field to include documentaries, there is one about everyone’s favourite second world war fighter, Spitfire, being released next month.

But these are outliers. Most Britflicks of the past 18 months have been middlebrow, mid-20th-century dramas. They have been set in the greenest and most pleasant parts of England’s green and pleasant land. They have been inspired by novels and true stories. And the characters have been well off, if not quite as aristocratic as those you would associate with the heyday of Merchant Ivory. There may be the odd lord and lady knocking about, but the protagonists usually see themselves as “just about managing”: the couple played by Andrew Garfield and Claire Foy in Breathe move to a sprawling country mansion, but they get it for a knockdown price, so they’re not that rich. In general, these films paint a cosily positive picture of yesteryear: imagine the bunting-festooned patriotism and retro chic of an episode of The Great British Bake Off shot at Dreamland in Margate. Whichever traumas and dangers they portray are offset by the comforting sight of Domhnall Gleeson or Tom Hollander in a V-necked jumper and flannel trousers, strolling through a meadow.

For the reasons behind this trend, look no further than the potential audience, says Damian Jones, producer of Goodbye Christopher Robin and the 2016 big-screen Dad’s Army spin-off. “What’s been bubbling for a while, probably since The Iron Lady and The Best Exotic Marigold Hotel came out [in early 2012], is the conviction that the most reliable cinema-going audience are the over-50s. And a period movie falls into the category of films that audience will go to see.”

Financiers are responding, he says, to the fact that younger viewers are either sticking to superhero blockbusters or staying at home to watch Netflix. “You’re always hoping that word of mouth will broaden the audience to other ages and demographics,” says Jones. “But the weekday matinee for older audiences has become key to British film’s economics.”

As for what those older audiences are getting from their matinee outings, the obvious answer would be that they are spending the “grey pound” on nostalgia. Chris Curling, who produced The Bookshop, disagrees, saying his film has “already done exceptionally well in Spain and Germany, and that can’t be down to a nostalgia for an England that is no more”. Nonetheless, Curling’s next production, Trautmann, is set in the same period: it is a biopic of Bert Trautmann, a former Luftwaffe paratrooper who becomes Manchester City’s goalkeeper shortly after the second world war.

“It’s about reconciliation and overcoming prejudice and being open to immigrants,” he says. Yet it is hard to shake the suspicion that many of these films’ fans are also fans of Brexit. Recall, if you can stomach it, the photo of Nigel Farage posing next to the Dunkirk poster and urging “every youngster” to see it. And, needless to say, almost all the characters in these films are white, the salient exceptions being the respectful Indians in Viceroy’s House and the respectful black Londoner (Ade Haastrup) who trades Macaulay quotes with Churchill on the tube in Darkest Hour.

“Brexit plays a part,” admits Stephen Woolley, who produced Their Finest and On Chesil Beach, “although Their Finest was very much a ‘remain’ movie. We enjoyed making it because of its lack of jingoism.” (Last year’s other Dunkirk films, he adds, were “slightly more generic although very well made”.) The irony is that while the British film industry is overwhelmingly pro-EU, not least because of the £300m of European funding it has received in the past decade, its evocations of a sun-kissed, pre-Common Market past are embraced by leave voters.

Or maybe they are being embraced by viewers who aren’t quite sure whether they should have voted leave or not. Dr Paul Elliott, who lectures on British heritage cinema at the University of Worcester, believes that, to understand the appeal of such films, you have to see beyond the vintage costumes and the picturesque fishing villages, and focus instead on the “simpler ethical framework” they construct. “We are in a period of political and cultural moral complexity where people don’t know what to think, so we look to films to give us that sense of orientation, that sense that there is a clear choice between right and wrong. Films set in the second world war and the postwar period offer that, because you knew who your enemies were. It’s seen as being a more consoling time – not that it would have felt like that if you were living through it.”

Indeed, Elliott argues that today’s heritage movies provide older audiences with the same reassuring good-v-evil certainty that the aforementioned superhero movies supply to a younger crowd. “Dunkirk is in essence a superhero film, which is what Christopher Nolan does best,” says Elliott. “It creates a very attractive binary moral image of law-abiding citizens coming together against an evil empire. If you swapped out the khaki for Lycra and the spitfires for spaceships, you’d have Avengers Assemble.”

But perhaps there is another, simpler reason for the industry’s fixation on the heart of the 20th century. Perhaps the reason is that Britain excels at heritage movies and no one can remember the Victorian era any more. “We like to tell stories about our parents and their parents, and the 1960s were 50 years ago,” says Woolley. “We’re all getting older.”