AS James McAvoy was saying to me just last week (sorry to startle you; that noise was merely the dull thud of an outrageous name drop), celebrities are overly sanitised these days, too PR-ed.

Mr McAvoy, who was himself extremely well groomed and besuited, was lamenting the fact the famous are given pelters for bad behaviour. Like Mark Wahlberg, he said, who appeared a little drunk on the Graham Norton show earlier this year, and received a cool reception for his shenanigans.

But it's no wonder the great and good are so keen to conform: on Planet Fame you're damned if you do and you're damned if you don't.

Justin Bieber, for one, seems determined to enjoy his fame and good fortune to the very best of his ability. This week he was pictured taking a sojourn to the Great Wall of China. But, unlike the rest of the tourists meandering merrily over one of the world's greatest architectural triumphs, Bieber had a piggy-back up the monument from his body guards. Fans expressed digust at his diva ways.

Who are they kidding? If I was a celebrity I'd want the Great Wall of China broken down and recreated, brick by brick, in a location of my convenience. I'd do my bit for charity, of course, but what's the point of building up a devoted legion of screaming fans without taking full advantage of the perks before Lady Fortune ages and withers before your eyes and you're left bankrupt in an ex-council flat in Scunthorpe?

Miley Cyrus, pictured, who has long ceased aquaintance with good taste, is clearly working on this principle. She has entirely lost the plot, if you read certain mid-market publications, what with the drugs, the stick out tongue and that foam finger. Sinead O'Connor certainly thinks so. The veteran performer, who has been there, done that and never twerked a single moment, has written an open letter imploring Cyrus to, essentially, sort it out.

Sinead fears, quite rightly, that Cyrus is hanging her coat on the shoogly peg of exploitation and pleads with her to put the coat back on. Or any clothes. To just put some clothes back on.

And here I think we have solved the problem. Not for celebrities to don more clothes. Like that would happen. Celebrity mentors. There's a fine line between mildly drunken entertainment and full-on car crash.

Sinead for Miley. David Bowie for Justin Beiber. Moira Stewart for Rihanna. Let me just run it past my new pal James.