Let’s get down to business straightaway. The good news is, there’s a flat for sale on Ennismore Gardens, a rather swanky square in Knightsbridge where people tend to buy, then just cling on. The slightly less good news is that clinging on here will cost you about £250,000 a year for the remaining 18½ years of the lease.

If you noted that figure without wincing, and perhaps even thought it sounded a bargain, you are probably safe — and certainly wealthy enough — to read on. Otherwise, you might care to look away now, because we’re about to reach the bit where the estate agent explains that, £250,000 a year or not, the flat will probably be used as a second home. Possibly even a third home.

“We’ve had interest from Russian and Indian businessmen,” says Ed Mead, of the estate agent Douglas & Gordon, which is selling the lease for £4m. “That’s the way it’s going. It used to be old money on this square. These days, it’s new money.”

For the past 26 years, the flat has been the home of Peter and Virginia Yates. Peter is rather celebrated in his field, although if the flat appeared on Through the Keyhole, the television game show, you might struggle to guess which field.

There are absolutely no obvious clues here to the couple’s background. The flat is rather formally decorated. Huge tapestries hang on the walls in the spacious reception hall, alongside Palladian prints. Once, there were pink flamingos on the walls, but they have long gone, and the furniture is so solid and respectable, you could take it home and introduce it to your parents.

It’s only when you get downstairs to the kitchen and happen to nose behind a door that you get the first clue: four Oscar nominations; two certificates each for The Dresser and Breaking Away. On the wall opposite, among the family photographs, is young Miranda Yates, the couple’s daughter, with a vaguely familiar figure. Ah, yes, of course — Steve McQueen.

“I was very worried about that photograph,” says Peter, now 79. “I thought, ‘Oh, God, she can’t be an actress.’ We tried to persuade both the children against becoming actors. It’s fine if you have terrific talent, but very few people have that, as well we know. And there’s so much rejection as an actor: one doesn’t want them to be miserable”. So, Miranda is a psychologist, while her brother, Toby, is a film editor.

Their father began his career as an actor, but soon discovered there was no money in it. So he became a director. After a spell as an assistant director, his first big film in charge was Summer Holiday, starring Cliff Richard.

He was highly praised for his work on The Dresser, with Eileen Atkins and Tom Courtenay (who have both been to the flat), but is perhaps best known as the director of Bullitt, which not only stars McQueen and boasts one of cinema’s best-known car chases, but was the first film to feature the police officer as antihero — not only fighting crime, but struggling against the police chief.

“Steve was worried about playing a cop,” Peter says. “One had to find a way in which he could play it, but still find original character and humanity. One had to persuade him that the good he would do, by making a policeman attractive to an audience, was important.

“People always tell me he was quite difficult to work with, but he was wonderful with me. We were literally writing the film as we went along — day by day. In the study, I’ve got three bound versions of different Bullitt scripts: the one I was sent, the one we rehearsed, and one that actually went into the film.”

Virginia and Peter, who met on The Guns of Navarone (he was assistant director, she did the publicity), have spent their lives moving about for work — London, New York, Los Angeles and, occasionally, a holiday home in the south of France. Now they want to be in New York, closer to their children and grandchildren. They have an apartment in the Dakota building, near Central Park — where John Lennon was shot and where Yoko Ono is still one of the neighbours — and a home in Los Angeles, in the style of a Normandy chateau, which they are also selling, for £1.25m.

“Los Angeles is a weird place — a company town,” Virginia says. “You’re always in the car. But the house is in Beverly Hills and within walking distance of a few things. We used to own a place up in the hills, which we sold 10 years ago.”

The couple paid £165,000 for the flat on Ennismore Gardens when they arrived in 1982. “We’d been out of London for 15 years, and we decided we wanted somewhere in the city,” Peter says. “Our apartment in the Dakota building had huge rooms, and we were looking for something similar. I opened the door here and said, ‘That’s it.’ The whole place has a feeling of size and air.”

The flats were built in the 1870s, using stone from the building company’s previous big job — knocking down the old Blackfriars Bridge and building a new one. The couple still have the original plans, showing a morning room and a boudoir. The first resident was an officer in the Crimean war who became a member of parliament, and the neighbours included two dowager countesses, a director of the Bank of England, a former first lord of the Admiralty and a golfing baronet.

These days, the inhabitants are much more international. “There are a lot of Americans, who all want to get involved in the life of the square,” Virginia says.

On the raised ground floor are the large drawing room, a study, a large bathroom and the main bedroom. A staircase leads downstairs to a dining room, kitchen and second bedroom. There’s also a small garden.

The estate agent’s details mention in particular that it’s handy for Harrods. Perhaps more attractive to the director of Summer Holiday, however, it’s only a short walk to catch the No 9 bus. That’s the one Cliff Richard drove to Athens all those years ago. These days, it stops at the Aldwych, which isn’t quite the same.

The lease of 16 Ennismore Gardens is for sale for £4m through Douglas & Gordon; 020 7225 1225, www.douglasandgordon.com

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