Dear Bono: From Bob Dylan to Mick Jagger to David Bowie, rock stars and films don't mix. So why is the U2 megastar acting in a film about Rob Roy, of all people? Give us a break, says a tired Bono-watcher

Great news. I see from the papers that, at the suggestion of Frank Sinatra, you are about to join that time-honoured tradition of old rock stars humiliating themselves in ridiculous Hollywood movies.

Who could forget your old mucker Bob Dylan, for example, in that immortal classic Renaldo and Clara? Or Mick Jagger in Ned Kelly? Not to mention David Bowie in . . . well, all of them really - Just A Gigolo, The Hunger (especially the cello scenes) and Merry Christmas, Mr Lawrence.

Anyway, the word is that you're going to be playing alongside Liam Neeson in a film about Rob Roy. Not Rob Roy the famous horse (now that would be something) but Rob Roy the swashbuckling 17th-century Scottish rogue (shades of Annie Lennox's career-ending role in Revolution), a sort of Robin MacHood.

It's hard to imagine really - you frolicking around the Highlands complete with Scottish accent, sword, kilt and no knickers. But then you're probably used to that, crazy, wild man of rock that you are.

Exactly why are you doing this, Bono? You don't need the money, that's for sure. Is it your reinvention thing again? I do hope not. Don't you realise that you can call yourself MacPhisto, you can call yourself The Fly, you can name-drop fashionable people like Brian Eno, Anton Corbijn and Paul Oakenfold till you're blue in the face but you'll always be the same silly old Bono to me. The man, like the haircut, remains the same.

I can't wait to find out who you're playing in the film, though. Liam Neeson's got the lead, so you're not Rob Roy, but then rock stars only ever get cameos. In my history book, it says that in the 1660s our hero enjoyed a brief period of repose as a 'grazier' at a place called Balquhidder. Maybe you could be one of Roy's sheep. Complete with Armani sunglasses, of course.

It's a shame you didn't get the lead, though, honestly it is. All Rob Roy's legendary acts of humanity, his generosity to the poor. That would have suited you down to the ground. Did you ever actually give any money to Sarajevo, by the way? Or did you just ring up and offer your sympathies? In front of an audience of thousands, of course. I can't remember whether that was before or after you ordered pizza for the entire audience. Ironic or what.

No, I reckon you'll probably be the Duke of Montrose, Roy's arch enemy, a sort of Scottish Sheriff of Nottingham. It would make me laugh, anyway. And I doubt if it would cause Alan Rickman too many sleepless nights.

It seems that you and Frank Sinatra bonded after you sang a track on Duets, even though it was recorded in separate studios - but then, hey, who gets to meet Sinatra? At least he'll be pleased to see your film career taking off. I don't actually think it's such a bad idea, either. After all, anything that keeps you out of the recording studio is fine by me.

(Photograph omitted)