Why do actors and actresses have sex with each other?

The answer seems obvious: because they can. Most actors and actresses are better-looking than average, with bodies they spend a lot of time starving and pounding into shape, so they’re not short of offers. And if you were kissing George Clooney/Scarlett Johansson/Ryan Gosling/[insert your personal favourite] on a film set all day, wouldn’t you get just a little bit frisky and keen to try some extracurricular practice?

Affairs between lead actors and actresses are the stuff of legend: Mary Pickford and Douglas Fairbanks, Clark Gable and Carole Lombard, Katharine Hepburn and Spencer Tracy, Bogart and Bacall, Simone Signoret and Yves Montand, Taylor and Burton, Melanie Griffiths and Antonio Banderas, Pitt and Jolie, Daniel Craig and Rachel Weisz. … Many directors encourage it for that extra verisimilitude in the performance. Besides, no matter the cultural credentials we as audience may claim, we turn up at cinemas in droves to watch the actors we would like to sleep with – so it does no harm to box-office receipts if the gossip mags confirm they are indeed highly sexed.

Scientists at Newcastle University have researched the personality types of actors and compared them with the general population only to find that they are A/ more extravert than the rest of us (which figures); B/more open to new experiences (I guess they have to be); and C/are much more narcissistic and neurotic than the average (ah-hah!). Maybe it’s that mixture of narcissism (“How wonderful am I!”) and neuroticism (“Can’t you see how wonderful I am? Do you not love me? Does the public not love me?”) that explains the need for the ego-massage of an affair with someone equally as hot as yourself.

I imagine the problem lies in distinguishing ‘real life’ from scripted make-belief. Do they fall for the other person or for the role they are playing? If they want to stay together, how do they make the transition into domesticity? What do they make of each other’s morning breath and the stray pubic hair in the shower?

UnknownCleopatra director Joe Mankiewicz described Burton and Taylor as not so much lovers as “two actors who didn’t know how to get off stage because there wasn’t a scriptwriter around to show them how”. And so they carried on with the performance through fourteen booze-fuelled, tempestuous years.

Burton had his feet slightly more on the ground with his Welsh valleys upbringing, but Taylor had been acting out the fantasy of ‘life as a Hollywood script’ from the age of ten. She hadn’t been exposed to anything else and it meant she would forever be choosing princes who couldn’t actually live up to the hype. She persevered through eight husbands and countless lovers but none could cut the mustard so she hankered after the ones she couldn’t have – Mike Todd, who died in a plane crash; and Burton, who got himself off the booze and found a flesh-and-blood intellectual equal for his final marriage.

Of course, actors and actresses are subject to all the usual complex reasons why any of us have sex with anyone else; but some of them make it much more tortuous – and a damn sight more public.