It is significant that such an unrepentantly quick-witted man should be at work anywhere in American TV. That he should have been (until recently) the top-rated chat-show host and remains a key figure in the war between the networks is little short of miraculous. Watching Letterman film his show in New York last year, what came through most strongly was the extent to which he is not only popular but revered. In the middle of the most severe snowstorms in living memory, people had driven halfway across the country to see him throw snowballs at his iconically annoying stooge and bandleader, Paul Shaffer. You might have said his audience looked up to him like royalty, but their attitude was just too respectful.
The strange truth is that for all the supposed dumbness of American TV, in the USA - in sharp contrast to Britain - intelligence is not inversely proportional to ratings. Why else should Letterman and Seinfeld top the US light-entertainment tree, while we have Noel's House Party and 2.4 Children?
Small wonder then that a succession of brave pilgrims should have found this sufficiently embarrassing to want to attempt to import the Letterman style to Britain. Jonathan Ross was the first to try, and in doing so changed the language of British TV. Danny Baker failed so badly that the whole idea of the chat show became discredited. It became so humiliating to us that we could only tolerate it through a protective screen of satire.
While it would be premature to declare the Mrs Merton/Alan Partridge/Edna Everage era at an end, the tide does seem to have changed in recent weeks. With the pain of the Gaby Roslin experience still fresh in their memory, Channel 4 has courageously (albeit quietly) shuffled on to the screen two new contenders for the vacant British Letterman crown. Both acknowledge transatlantic inspiration - Johnny Vaughan's nattily roguish Here's Johnny in its titular nod to Johnny Carson's old introduction; and Bob Mills's bizarre The Show, in its crazed determination to be a real-life Larry Sanders. Both shows exbihit hopeful signs of finding their feet.
But these two mercifully improving programmes are, it turns out, merely appetisers for the imminent main course. Behind closed doors in the media- whore-strewn streets of Soho, a group of dedicated people are striving to build a British alternative to the five-nights-a-week Letterman experience. Four weeks before it takes to the airwaves on Easter Sunday, Channel 5's flagship late-night chat show, The Jack Docherty Show, is slowly being taken out of its mental packing cases. The eponymous host - a tall Scottish man, vaguely but not offensively familiar from previous TV appearances on the BBC2 comedy show Absolutely and occasional stints on Edinburgh Nights - makes a good case for his show's right to exist.
"I think it's something we've always missed in this country," Docherty claims. "I like the idea that you tune in every night to this guy who's sort of your mate." Why does he think it's never been done here before? "I think because the only way it can be done is with a new channel - otherwise there's no way to free up the schedules for it."
There are plenty of reasons why it might fail. The cult of celebrity is not so far advanced in Britain as it is on the other side of the Atlantic. "A big guest causes real excitement there," Docherty observes enviously. "Here it'll be [adopts non-committal tone], 'It's David Jason ... oh good'." People are likely to be more resistant to the host's authority as well, especially as Docherty admits to having no experience as a stand-up comedian, and jovially claims to be approaching the crucial opening monologue as "a massively public Comedy Store open-mike spot".
On the surface then, the omens are not good. But watching a shoestring pilot show (the traditional band replaced by an endearingly forlorn man with a drum), there is an intriguing sense that Docherty just might have what it takes to pull this off. He has much of Letterman's comical physicality, with none of his occasionally annoying tendency to chase his own tail at guests' expense. He is cheeky without being rude, confident without seeming arrogant, and while the set is entirely on the standard American model, the show seems to derive strength from that rather than being held back by it.
But won't the success of recent chat parodies make it difficult to take The Jack Docherty Show seriously? "These things co-exist," Docherty insists."I don't think Larry Sanders emasculates David Letterman at all - they feed off each other." What people enjoy about the "real" thing is the artifice, while the spoof makes fun of the emotional reality that underpins that artifice. You can't have those two pleasures at the same time - that's why the Bob Mills show doesn't quite come off and nobody buys Tony Ferrino records: it's the buffer at the end of the tracks of post-modern TV entertainment.
Ironically, The Jack Docherty Show's biggest asset might just be that most oft-derided of all showbiz staples - sincerity. "I'm going to assume that whoever I'm talking to, someone watching is a fan of theirs," Docherty says. Is taking the bit of himself that is a chat-show host and losing the rest something he's always wanted to do? "It was never a great ambition of mine," Docherty laughs, "and if somewhere down the line I can recreate that feeling - that I don't give a shit - the show has a chance of being a success".
'The Jack Docherty Show' starts on Channel 5 on Easter Sunday at 11pm.