After 50 years in showbiz, Dame Edna hung up her ballgown and retired. It turns out she's been travelling aboard a luxury yacht ever since and she now invites us on for this chatshow special with Sharon Osbourne, Judge Rinder and Emily Atack, subjecting them to her cheeky interviewing style.

Dame Edna Rules the Waves, BBC1, review

Sharon Osbourne and Rick Stein were among the guests but this was, as ever, all about Dame Edna.

Chat shows can sometimes throw up guest lists that read like a particularly demented dinner party and that's certainly the case with Mr Norton tonight as Hollywood hell-raiser Colin Farrell, Top Gear motormouth Jeremy Clarkson, X Factor matriarch Sharon Osbourne and comedian Jo Brand find themselves parked next to each other on the sofa. At least we get a rare chance to sample the live delights of chart-topping Arcade Fire on terrestrial TV.

Let's hope chatty Alan has been sharpening his tongue over the summer ready to welcome in the first batch of guests for his 11th series. There's plenty of juicy material for him to get stuck into, what with a quartet of Dragons - Peter Jones, Duncan Bannatyne, Deborah Meaden and new business top cat Kelly Hoppen - plus comedian Lee Evans, actress Keely Hawes and reheated X Factor judge Sharon Osbourne. He'll eat them all for breakfast. Rizzle Kicks provide the music.

The phrase "celebrity roast" sounds like either an inspired idea for a bonfire, a romantic date with a footballer and his friends or some nightmare series, no doubt soon to be commissioned, in which minor soap stars share their favourite recipes. In fact, it refers to the practice whereby a group of comedians takes turns putting down a well-known entertainer as well as each other.

That's what the roast became in America, where it was popularised by Frank Sinatra, Dean Martin and Sammy Davis Jr. Last week, we got the British version, A Comedy Roast (C4), in honour of, respectively, Bruce Forsyth, Sharon Osbourne and Chris Tarrant. For reasons of national morale, it doesn't do to dwell on the difference between those two sets of names.

However, the thinking appears to be that what the show lacks in personalities, it can make up for in vulgarities. Sometimes, that tactic worked under the caustic stewardship of Jimmy Carr, who looked as demonically thrilled as a class clown given permission to swear at his teachers. Carr was responsible for most of the moments of comedy that produced not a laugh, but a gasp, including a joke about Tiswas being the second biggest thing that Lenny Henry had ever been in.

More often, the coarseness was cover for an overreliance on the autocue. As much as he sometimes struggled with reading lines, Dean Martin was never known to resort to the c-word on US TV and nor, come to that, did anyone ever accuse Sinatra of mistaking breast milk for "man gravy". A dry roast this wasn't.

Yet the biggest failing was that no matter how crude the insults served by Jonathan Ross, Jack Dee and a variety of comedians, no one, including the guest of honour, had heard of, none could match the flame-grilled indignity of taking part in the show. A roast that was all sauce and nothing to savour.

And if we're looking to invent new words and phrases, how about "Crap as A Comedy Roast"? You'd use it to describe something that was as awkward and contrived and joyless as Jimmy Carr and chums spending an hour taking the p*** out of someone semi-famous sat opposite them on stage.

"Roasting" is an American tradition: being brutally but lovingly rounded upon by your peers while taking it all with benign grace - think: This is Your Life, You Stupid T***. The US TV version of this features some of the most staggeringly lewd, vicious punchlines I've ever heard, the enormous capacity of Pamela Anderson's vagina, for example, being a recurring theme on hers.

So what was in store for Bruce Forsyth, Sharon Osbourne and Chris Tarrant? Uncomfortable oddness, really. Jonathan Ross visibly rattled Brucey with some opening salvos: "He wasn't a pretty baby," he tells the audience, "but he did grow up to be a f***ing ugly adult." What else? Oh yeah: "When the dinosaurs died out, he was taken in for questioning." Arf! The weird thing was that most of the roasters were just typical gun-for-hire, Channel 4-type comedian fodder. Paddy McGuinness did a nervous Who Wants to be a Millionaire? skit on Tarrant, who looked so prickly throughout that you suspect Alan Partridge would have taken a roasting better. Jack Dee slagged everyone off and looked sadder than usual to be doing it. There was one quite funny joke about it being hard to believe the real Sharon Osbourne is here tonight, "because the real Sharon Osbourne is in a black bin bag round the back of a plastic surgeon's in LA!. And she took it all quite well, mainly because she just hooted like as sozzled nan the entire time.

Maybe everyone else loved it. It just seemed weirdly open and honest. I thought the whole point of being British is that we repress our true feelings, so that when they do pop out they're disguised, perhaps in the form of a witty joke or a song or a droll suicide note. Alternatively, we could just stick to slagging people off behind their backs so that we don't have to pretend to hug them in front of Jimmy Carr afterwards. I don't think A Comedy Roast suits us. If someone can work out a passive-aggressive equivalent, however, we may be in business.

Based on an (apparently) successful US model, the UK version of A Comedy Roast sees a parade of utterly uninteresting "celebrities", faux-insulted by a panel of comedians in a kind of This Is Your Life for the Big Brother generation.

Anyway, last night was Sharon Osbourne's turn. Presumably, her casting had more to do with her availability than her suitability; there can be little other explanation. No one, bar no one, needs to hear another word about her, even if it is from the pleasingly snarled lips of Jack Dee.

It's a shame, really, since some of the gags weren't bad at all. Patrick Kielty gave a particularly enjoyable turn. Who knew he could be so vicious? Even Gok Wan, who surely ranks close to Sharon Osbourne in the overexposure stakes, was pretty good. No, the problem isn't the jokes. It's their subject.

Given the level of venom each episode's victims have to tolerate, it seems unlikely that the show would attract anyone but the desperate or the egotistical. Both of which, frankly, I could do without.

In a merciless variation on a tribute show, a host of comedians and celebrities line up to lampoon Sharon Osbourne. At the start, the host Jimmy Carr compares her to the Queen. "Her children are dysfunctional. Her husband is incoherent and nobody is really sure what she does." Thereafter, the likes of Alan Carr, Ronni Ancona and Louis Walsh take to the podium and let rip about her age, her plastic surgery, her husband, her incontinent dogs, her foul mouth and her fashion mistakes, while she sits at a table and cackles loudly. The highlights of the evening are Ancona reading extracts from Osbourne's new novel, Revenge, and Patrick Kielty risking his life to mock her parenting skills. "What a delightful evening it's been," says a glum Jack Dee.

It's a fate you wouldn't wish on your own worst enemy: Bruce Forsyth must have done something very bad in a former life to have his recent gruesome grilling by Piers Morgan, a man who insists on probing where no one wants to go, swiftly followed by the undercooked fawn-fest that was Bruce Forsyth: A Comedy Roast.

Starting with the dreaded words 'please welcome your host... Jimmy Carr!', a phrase guaranteed to have me instantly gagging (but not in a good way), C4's resident Smug MC, a ventriloquist's doll in human form, launched into his unique brand of makes-you-want-to-slap-him charm. 'A roast is like good-natured bullying,' he smirked. 'Good-natured in that it's happening to someone else, not you.' Unbelievably it was downhill from there, a gruesome selection of backslapping/stabbing blokes taking turns to out un-funny each other. Jonathan Ross started off with his tired effing and blinding routine, clearly miffed he wasn't talking about his favourite subject (himself). No, he was there to dishonour Bruczie, so what did Ross's rapier-like wit conjure up? No idea, it was instantly forgettable, other than setting up the night's weary theme: wow, Bruce Forsyth is, like, really old. He's done lots of dodgy gameshows. And he's got a chin. And a beautiful wife. Satire it wasn't.

Jimmy Hill's chin twin guffawed through gritted teeth throughout, taking it on the proverbial. But his lizard-like stare needed double-glazing to get through the kill-the-room combo of Bruno Tonioli and Arlene Phillips, whose contribution was up there with such classic double acts as Sam Fox and Mick Fleetwood and Rula Lenska and George Galloway for making you want to stab your eyes out.

All this crackling-free, toothless 'roast' proved was that the more people ho think they are funny there are in a room, the less likely you are to have a laugh. Only Sean Lock emerged with dignity intact but his best line - a dig about being surprised that Ross turned up in person instead of persecuting a national treasure by phone - was all over the trailers, so you'd heard it anyway. Next up it's Sharon Osbourne then Chris Tarrant - truly, C4, you are spoiling us.

A comedy roast is a prolonged mickey-take of someone while that someone is still in the room to enjoy the jokes, but from the very first of Jimmy Carr's opening remarks it's clear Sharon Osbourne has her work cut out. The jokes are savage and the language is terrible, as Patrick Kielty, Alan Carr and Jack Dee rip into the former X Factor judge's parenting skills and plastic surgery.