Last Night's TV - David Walliams' Awfully Good, Channel 4; The Secret Mediterranean with Trevor McDonald, ITV1

You need a bit of nerve if you're going to present a compilation of "compelling car-crash TV moments". The job, essentially, is smirking at the shortcomings of others, while trying not to look like a condescending twat. And while this isn't actually impossible (think of the way in which Harry Hill manages to finesse the task with some kind of affection), it's a lot harder if there's even the faintest possibility that one of your own programmes might one day be a candidate for some future "library of low points". Surfing in on a tide of distinctly underwhelming reviews for Come Fly with Me, David Walliams hasn't been very lucky with the timing of David Walliams' Awfully Good, particularly when it comes to remarks about the casual racial stereotyping of Eighties comics. There are people who might be able to get away with goading Jim Davidson with the back-announced invitation – "Go on... do de Chalkie voice" – but right now Walliams isn't one of them. Do the Moses voice, David, go on.

His response might be that this wasn't Walliams at all anyway – but a kind of parody of a cheesy television host – complete with dinner jacket and showbiz schmooze. "Welcome to my world," he said at the beginning, "the wonderful world of television", and it looked for a while as if he'd adopted Bob Monkhouse as his target, all perma-tan and ersatz conviction. But then sarcasm doesn't sit easily with such character comedy. It may be the lowest form of wit, but it is also an essentially sincere one (the reason Charlie Brooker's sarcasm is funny is that you know the rage is real). And sarcasm is essential to such things. So here Walliams flickered oddly in and out of register, at one moment camping it up wildly in costume, at the next being himself on the voiceover, hinting at a solidarity of knowing mockery between us and him.

The mere passage of time accounted for the majority of the clips, since almost all television looks a bit clunky and gauche once it's spent a couple of decades in the vaults. Right now I suppose it's conceivable, for instance, that Famous and Fearless – Channel 4's bloated live arena show – looks cutting edge. But give it 20 years and its essential tackiness will be obvious to even a five-year-old – today's fashions in bombast and clothing and celebrity worship having curdled into yesterday's crass notion of production polish. And that's even without the possibility that something goes badly wrong in mid-transmission – the justification for a literal piece of car-crash television that featured here, when Noel Edmonds had to cut away from a Late, Late Breakfast Show stunt going drastically wrong to the breezy clichés of his closing script. I wonder if Chris Evans has rehearsed a couple of quips to cover the arrival of a resuscitation team?

Quite a few of the remaining clips could be filed under Inadvertent or Subversive Suggestiveness, which has only a limited appeal. One assumes the adults who worked on the Play School episode, featuring a dog called Boner, knew precisely what they were about, but what they were about wasn't that clever. And at least five percent of the examples weren't terrible television at all, but quite good television about slightly jaw-dropping subjects. With slightly tighter quality control it could have been a half-hour programme, though it's only fair to add that it would have made you laugh quite a lot at that length. Walliams' highlight was an underpowered moment from Tiswas. I would have gone for the stupefying scene from Doctor Who in which the Doctor appeared to fellate a large green alien or the Tomorrow People's attempt to inject a bit of Holocaust awareness into a children's sci-fi show. "Oh no, Mike, no," said one character solemnly, "Hitler isn't dead. Hitler is Neebor from the planet Vashir... a galactic, shape-changing psychopath." Or perhaps, for the more upmarket connoisseur of Bad Ideas, the sequence in which Simon Callow performed Shakespeare's Sonnet 116 as a jazz jam session with John Dankworth and Cleo Laine. My toes still haven't entirely uncurled.

ITV's World of Sport featured in Awfully Good, though I thought its live coverage of caber tossing and caravan racing looked absolutely terrific. You could imagine Dickie Davies anchoring an equally intriguing OB from the Turkish camel-wrestling championship that featured in The Secret Mediterranean with Trevor McDonald, in which the former newscaster flits about the Med failing to rise to the occasion. Off the French Riviera, he paid a visit to the Christina O, the super-yacht once owned by Aristotle Onassis, which can now be chartered out by rich glamour-seekers and when he was told by the executive chef that the guests could be very demanding, McDonald simply sympathised with him politely, rather than pressing him for some gratifyingly outrageous specifics. Offered the opportunity to sample camel sausage, he turned it down (surely an elementary failure of journalistic duty), and in Venice he appeared startled that the local gondoliers wouldn't have been welcoming the first woman to get a licence. "It's so unmodern to have that kind of attitude really," he said. They're taxi drivers, Trevor, and what's more they're taxi drivers whose vehicle hasn't changed much since the 17th century. Being unmodern is what they do for a living. But even better was his probing inquiry to a city official who was explaining how the Piazza San Marco is regularly flooded at high tide: "It's one of the problems of this city isn't it... the water?" Nothing gets past him.