The most cherishable moment in Jon Ronson's Witness film about Omar Bakri Mohammed, The Tottenham Ayatollah (Channel 4), occurred during the video footage of a rally in Trafalgar Square. A large number of black balloons had been inflated to carry the message of Islam to a godless land. Unfortunately the text was too heavy, so instead of lifting to the skies in a glorious ascension the balloons merely bobbled and bumped around the feet of Dr Mohammed's followers, who kicked at them disconsolately in an attempt to impart some lift. It was the perfect image of fanaticism grounded by incompetence. If these people couldn't blow up a balloon properly, what chance had they of blowing up Western civilisation?

The really unsettling thing about the sequence, though, was that there was no way of deciding whether your laughter was a proper response or a comforting distraction from the odious ferocity of Mohammed's language. This was also true of the whole film, a very funny account of a man with unfunny opinions. Undoubtedly there was a rich comedy in seeing the scourge of Western decadence bustle out from a "secret" meeting to offer the film crew some "icey-cream". It is also true that his genial tour of the Wood Green shopping centre, in which he explained how Islamic law would affect the facilities, was a bit of a giggle, even for the fundamentalist himself. When he announced that the "Spicey Girls" would be arrested immediately, a little smile flickered through the undergrowth of his beard.

But then, just how seriously to take this man was at the heart of Ronson's film. By treating Mohammed as a real threat, perhaps the journalists who mob around him inadvertently create the monster they fear: an image of militant Islam which is disavowed by the vast majority of Muslims. Then again, how could you be sure? From some angles, that dishevelled German fellow who went around Soho in the last century boring on about class war probably looked like a harmless clown too.

Jon Ronson, who knows exactly what he is doing in these things, adopted the comic pose of a man out of his depth: "Somewhere along the line my role has shifted from journalist to chauffeur," he noted drily after he had been press-ganged by Mohammed into driving him to Office World. And though he fretted mildly about concealing his own Jewish background, he left the real job of fulmination to Rupert Allason, the Conservative MP, who has been campaigning against Mohammed's exploitation of the benefit system.

This offered a different comedy - that of xenophobic alarmism - and it was perfectly pointed up by one of the Tory faithful who offered a quiet riposte to Allason's crowd-pleasing indignation. "Well, it's a free country," he said calmly, "I don't think he'll get very far".

The reception for Channel Five is so bad where I live that I can hardly bear to watch. But I have been braving the ghosts and hiccuping sound to see how their ballyhooed news programme has been doing. Hardly surprisingly, it turns out not to be a radical innovation at all, but a version of a news bulletin that has been around for years; it's called Newsround and it goes out as part of BBC Children's Television.

The comparison isn't an insult, by the way: Newsround is a crisp, competent show which has a precise idea of what its constituents want. Channel Five's version doesn't quite match the original yet - though with a little more editorial ambition, its First on Five reports (longer films off the daily news agenda) might just shake up the opposition. It also has a big plus in the shape of Kirsty Young, who is excellent - attractive and composed. She can also keep a straight face, which is handy because some of the reports she cues in are a scream - hysterical with the desire for difference. Reporters turn up goose-pimpled, a cold wind whipping around their collarless jerkins or they flicker about the screen courtesy of pop video jump-cuts. Poor Chris Morris must weep when he watches - he might as well have been selling garden gnomes for all the impact he's had.