Even the most passionate aficionados of a ropey film - and I write as someone who owns two copies of Steven Segal’s Under Siege, putting me in a category which I can only share with Steven Segal’s mum - must have felt their hearts sink when it was announced that Madonna was directing a movie about Wallis Simpson. Madonna, let us be honest, has not often made the world of cinema a better place. She is a shockingly bad actor. If you need reminding, watch a few minutes of Dick Tracy (five minutes maximum, so you don’t start to cry). And the news from the Venice Film Festival seems to confirm that she’s no better behind the camera than in front of it.

Any sense of self-awareness would surely tell pop stars to run to the hills when Hollywood comes calling. It so rarely ends well. For every Will Smith, who converted a minor pop career into a major acting one, there’s a Whitney Houston in The Bodyguard. For every Oscar-winner like Jennifer Hudson (who first became famous by not winning American Idol), there are ten clunkers like Mariah Carey, whose debut film, Glitter, achieved an almost unbeatable 7% on the film review website, Rotten Tomatoes.

I still feel slightly queasy when I think of Sting in Dune, or David Bowie in The Prestige. The man who once fell to earth had the unenviable task of trying to make us believe that electricity could produce an infinite number of hats, and Hugh Jackmans. Even for the scientifically illiterate, it was risible.

And who could forget Christina Aguilera in Burlesque? Yes, that’s right. All of us, once we’d rinsed out our eyes and ears with bleach, and sworn on our mothers’ lives never to speak of it again.

As for successful pop star directors, I can only think of one - Barbra Streisand – who was both a genuine pop star and went on to direct a genuine hit. Unless you want to count Dave Stewart of The Eurythmics, whose directorial outing, Honest, is still spoken of as a measure of awfulness by film critics (pretty much the only people who actually saw it, and they were being paid to sit through it).

Even when things go the other way, and film stars decide to put an album out, the effects on their original career can be devastating. Jennifer Lopez is phenomenal in Steven Soderbergh’s Out of Sight. But a year later, she released her first album, and soon she was starring in Gigli, a film so awful that I can’t improve on its Internet Movie Database description: ‘The violent story about how a criminal lesbian, a tough-guy hit-man with a heart of gold, and a retarded man came to be best friends through a hostage’. Yes, criminal lesbians, and hitmen who have hearts of gold. Surely it’s time for a remake? I’m sensing a new project for Madonna.