Are the days finished when an inexperienced actress could be surprised with a tub of butter, as was 20-year-old Maria Schneider during the infamous sodomy scene (the unscripted brainchild of co-star Marlon Brando) in Last Tango in Paris?

The British tabloid press had one of its regular clammy spasms of outrage in November 1986, aroused by a shot of actor Patrick Malahide’s pale, naked buttocks bobbing up and down amid the bracken of the Forest of Dean.

In many ways, the furore over the sex scenes in Dennis Potter’s The Singing Detective marked the full extent of the Aids-panicked, neo-puritan backlash against nudity and coitus in film and on television. It is a pendulum that had been swinging since the 1970s, when Hollywood and then British TV drama started to disrobe and feign explicit sexual intercourse, and the past decade, when simulated (and un-simulated) sex returned to our screens with a vengeance.

Writers are coming up with more – and more graphic – sex scenes for directors to film and actors to perform. “So many scripts these days… you just can’t get away from it,” says Maxine Peake, who has portrayed coition in dramas as diverse as Shameless and The Secret Diaries of Miss Anne Lister. “I remember years ago reading scripts and thinking, ‘We’ll have a chat about this and hopefully it will go,’ but now they seem to be splattered everywhere.”

So what are the mechanics of simulating sex for the camera when titillation is not the primary ambition? What do the performers feel about doing it? And are the days finished when an inexperienced actress could be surprised with a tub of butter, as was 20-year-old Maria Schneider during the infamous sodomy scene (the unscripted brainchild of co-star Marlon Brando) in Last Tango in Paris?

“Marlon said to me: ‘Maria, don’t worry, it’s just a movie’,” recalled Schneider in 2007, 35 years after her mock lubrication and four years before her death. “But during the scene, even though what Marlon was doing wasn’t real, I was crying real tears. I felt a little raped.”

Such impromptu exploitation is unlikely to happen today, especially if the artist has a no-nudity clause in their contract – an arrangement more common in Hollywood than in Britain.

Andy Garcia, Julia Roberts, Scarlett Johansson and Sarah Jessica Parker are reportedly among those who refuse to be filmed naked, while Charlize Theron, Neve Campbell and Sharon Stone insist on a “nudity rider”, a contract that gives the actors the final cut of their love scenes.

For most actors, however, faking sex is a necessary evil.

“It’s very traumatic, it really is,” agrees Natalie Dormer, who played Anne Boleyn in The Tudors. “It never gets easier. That’s why it’s so important that you can trust in your writer and director, to make sure that it’s not just gratuitous. It’s like a full-over medical examination that we women have to go through at the doctors – never pleasant but for the greater good.”

Ruta Gedmintas lost her screen virginity to Jonathan Rhys Meyers in The Tudors. “I was absolutely terrified and had no idea what was going on,” she recalls. “I cried afterwards because I was thinking, ‘This isn’t acting, what am I doing? My mom’s going to see this.’ But now I’m very strict on what I do – I have to know that a sex scene is going to give the audience information about your character or a relationship. If it doesn’t do either of those, I won’t do it.”

Donald Sutherland once said, “When I take my clothes off people are no longer looking at me as a character, they’re looking at me with no clothes on.’ “ Sutherland was one half, with Julie Christie, of one of the screen’s most iconic couplings — the did they/didn’t they? (they didn’t) love-making sequence in Nic Roeg’s 1973 movie Don’t Look Now.

“I didn’t really give instructions,” Roeg recalled in 2006. “It was a scene of intimacy that required intimacy on the set. Not a lot of interference. A cameraman and myself. They were intelligent people… we only stopped in order to relight a scene and we’d talk together in the breaks.”

”They black out the set so it’s not just an open warehouse where there’s people getting a cup of tea when you’re doing it,” reveals Claire Foy, who starred in the series Upstairs Downstairs. “But it can never really be a small set – a small set on TV is a camera operator, a boom operator, a focus puller, the director…” And, adds Hal Sparks, one of the actors from the American version of Queer as Folk, there are all those people who might be watching on monitors, as well as any editors who later cut the film. “Ultimately, as far as who sees the raw footage… between 15 and 20 people are going to see you at your most vulnerable.”

The viewer, however, might not be getting the whole picture. Certain camera angles can trick the audience into believing that two actors are writhing around naked while in fact they both might be half-dressed. Harry Bradbeer, director of risk-taking dramas such as This Life, and BBC’s current lesbian saga, Lip Service, recalls a particularly explicit bath scene where one girl appears to shave the pubic hair of another girl.

“It was something (that seemed) very explicit but none of it was seen because we shot it carefully from either end of the bath,” he says.

Female actors might also wear body stockings, G-strings and breast-cups – or like Lara Pulver in the recent series of Sherlock, they might decide that the scene would be over more precipitously if they didn’t spend hours in make-up, and simply appeared as nature intended.

“The director said to me, ‘You can either spend hours shooting it to avoid seeing straps or we take all that off and shoot quickly.’ “

Men, meanwhile, can protect their modesty with what is called a “sock” (“It’s a flesh-coloured pouch that wraps your genitals up like a bag of leprechaun’s gold,” explains Sparks).

Mostly, however, the director will aim to block intimate body exposure with choreography. Not for nothing did Sharon Stone, after the three-day sex-shoot on Basic Instinct, describe herself and Michael Douglas as “the horizontal Fred and Ginger of the ’90s”.

The American actress Chloë Sevigny, who famously performed unsimulated fellatio on her co-star and director, Vincent Gallo, in the 2004 film Brown Bunny, says tight direction can take the tension out of performing a sex scene. “It was choreographed like a fight,” she says of her love-making scene with Hilary Swank in Boys Don’t Cry.

“The director will talk you through, so it’s, ‘Bring your hand down her back…’ things like that. Or they’ll say, ‘Now you both orgasm.’ It’s easier if someone is coaching you through it.”

And what of that co-star – is it better to know and like him or her? Or is it easier if the actors are strangers? Maxine Peake recalls shooting the 2005 TV movie Faith with Jamie Draven. “It was the first scene on the first day of filming,” she says, “and I was supposed to be having an affair with him – he was my sister’s husband – and I had to burst in through the back door with him, ripping each other’s clothes off and then end up having sex in the living room.

“I was shaking and pale – and I always remember him saying to me, ‘Hi I’m Jim… shall we just go for this?’ and I said, ‘Sod it, let’s just go for it.’”

Filming sex scenes with an actor who is a friend can be an awkward experience, or it could help things along.

Jamie Campbell Bower describes his love scenes in the racy American costume drama Camelot, with Tamsin Egerton. “I’d known her for years,” he says. “We grew up very close to each other and did local youth theatre together from about the age of 11. There was no mystery – we knew exactly who each other was.”

Although all actors interviewed claimed sex scenes were unerotic, apocryphal tales of male actors who can’t hide their arousal are as old as cinema. Says Sevigny: “There’s the famous cliché where the boys say, ‘Excuse me if I get hard… (and) excuse me if I don’t.’”

And while films where the actors have real, as opposed to simulated sex, are becoming more common – in Shortbus, for example, the French film Baisse-Moi, or Michael Winterbottom’s 9 Songs, which featured the first real male ejaculation in a mainstream movie – thespian lore is full of tales of actors getting carried away while simulating sex, and of actors suddenly wishing the love-making was for real.

Ultimately, the over-riding emotion is one of embarrassment, admits Cléménce Poesy, whose sex scenes with Eddie Redmayne in the recent adaptation of Birdsong provoked letters of complaint to the BBC. “You can’t really get over the embarrassment,” she says. “I know people such as Keira Knightley do things like drinking shots before filming, but I handle them by not really watching them afterwards.”

And there might even (whisper it) be the tiniest element of vanity involved. British actor Damian Lewis has had countless shirtless scenes in American thriller-drama Homeland, and has quite obviously been pumping iron in preparation.

Or, as Dormer says about being cast in Game of Thrones: “Oh God, here I go, taking my clothes off again; I’ll have to start running round the park again.” – The Independent