I don't believe it!

Whatever else he was, Tony Hancock was a master of exclamation - his rising yelp of incredulity or indignation often able to twist a laugh out of otherwise quite innocuous lines. Partly this was down to his face - a lugubrious mask which could deliver a veritable thesaurus of comic grievance: wounded pride, surprised disappointment, snubbed excitement and startled humiliation. The physiognomy was almost mask-like in its epitome of glumness - heavy eyebrows tilting downwards in the middle to reflect the familiar grumpy clamp of the jowled mouth, the eyes beneath, stricken or furious. He looked like a prince who has just realised that he has been turned into a frog and that no amount of kissing is ever going to reverse the transformation.

But Hancock constructed his fame on radio before he extended it through television, and it was the combination of facial passivity and the vocal jolt of animation that offered such a charge of comedy. His best-known lines all come with exclamation marks attached - "Flippin' kids!", "Cor. Stone me!", "That's a whole armful!". So I like to think of him, if he was still alive, watching a more recent star of exclamation, another actor who has managed to make private exasperation stand for something larger, and by doing so has won huge television audiences. There is something of Hancock in Victor Meldrew - indeed, one can almost imagine the lad from Cheam delivering Victor's trademark cry of despair at the grinding recalcitrance of the world, perhaps adding his own distinctive grace note - "I dooon't belieeeve it, mush!".

But the differences between the two characters are more instructive than the similarities. Where Hancock is all pretension and hope, Victor has no expectations. Hancock embarks on his new ventures, whether it's poetry or photography or acting, with a gleaming conviction of imminent success; in his misanthropic heart of hearts Victor knows that it is only a matter of time before something goes wrong, so that his shriek of incredulity actually reverses what he is feeling, that he can believe it only too well. Where Hancock caught the unsettled mood of postwar Britain, a compound of wildly utopian hopes and drab falling-short, Victor tapped into something sourer and more furious, the growing disenchantment with Thatcherite politics. Most crucially, though, and Hancock himself might have seen it had he lived, Victor was an invention quite distinct from the man who played him - not that eerie morphing of a real person into a comic personality.

Hancock was never going to make 75, of course. If he had, then he wouldn't have been Tony Hancock anymore. Not, at least, the constellation of received opinions which goes by that name today - in which the sad, vodka-sodden death is inextricably connected to the soaring arc that made him the most popular and best-paid comic of his day (rumoured to be paid over pounds 1,000 a programme, according to some breathlessly incredulous newspaper reports of the time). A Tony Hancock eking a living on nostalgia tours of the Pacific Rim theatre circuit, tapping the long memories of expatriates and Anglophiles, would not have satisfied our appetite for a martyr of comedy - a peculiarly English exemplar of the old cliche about the tears of a clown. It would also remove one of the artistic satisfactions of the Hancock story, which is that he was a performer who exploited his own disappointments for laughs before they finally overwhelmed him.

Some of the strongest comedy in Galton and Simpson's scripts for Hancock come out of the gap between aspiration and actuality, a theme peculiarly suited to Fifties Britain but one which also grew perfectly in the soil of Hancock's character. There's a good distillation of the effect in one of Hancock's lines from "The Poetry Society", after he rebukes Sid James's characterisation of the avant-garde group he has just joined as "a group of layabouts".

"We are not layabouts," Hancock replies, eyebrows flaring with indignation. "We are artists, mush." The sentence swells with aesthetic aspiration - and is instantly popped by the low vulgarity of the last word. Hancock would have been a happier man if he'd recognised that the first three words of the sentence were as essential to its comedy as the last, but in life he didn't. He ached to cross the gap that his scriptwriters so skilfully exploited, between what he might be and what he actually was, and ended by falling headlong into it.

"You tell Alan and Ray, either they write me up where I belong, or I get Eric Sykes," he protested to Dennis Main Wilson, his television producer, after becoming anxious that the character was becoming increasingly clownish.

Hancock himself called the brew of pomposity and humiliation the programmes created "Ancockism" and, in as much as it was inextricably connected with his name, that seems reasonable. But there is a good case for arguing that it would be more accurate to describe it as Galton and Simpsonism. The two scriptwriters wrote virtually every word Hancock uttered on radio and television between 1952 and 1961, and it was they who finally brought off the innovation of a star vehicle without interruptions from musical guests and without thumping punchlines. (Those who think Jerry Seinfeld invented the idea of a sit-com in which nothing happens should take a look at early Hancock's Half Hour - a highly successful performer playing himself as a less successful one, an establishment of strange sidekicks and friends, a willingness to build an entire programme without any plot at all.) This achievement depended on the canny overlap between Hancock's character and that of Anthony St John Aloysius, the distorted Doppelganger who appeared on screen.

When, a few years ago, Paul Merton attempted to remake some of the Hancock classics, the result was a failure - in part because the comic persona of a notable improviser seemed hemmed in and cramped by the scripts. Merton is never better than when he is ad-libbing but Hancock rarely strayed far from the reassuring guide-rope of the printed lines, and these lines were perfectly placed for his natural reach. If you aspire to artistry, however, artifice must play some conspicuous part in your achievement, and towards the end of his career almost everything conspired to remind Hancock that his gift was instinctive; not the result of labour or mental calculation but as divorced from any sense of achieved merit as the shape of his face. His first takes were almost always his best, as though conscious effort could do nothing to his performance but deplete it. His anxiety about learning lines, always a problem, grew until he was obliged to use telly-prompters or idiot boards, a concrete reminder that he was dependent on other people's lines (Hancock aficionados will point out, with the faint superiority of the true connoisseur, that the "Blood Donor" episode was actually marred by Hancock's reliance on off-screen cues, which gave his performance a slightly stiff and distracted quality).

Worst of all, his attempt to separate his achievement from that of his scriptwriters proved a darker truth. While they elaborated "Ancockism" into the subtler pathos of Harold Steptoe, in another hugely successful series, Hancock himself worked on increasingly unsatisfactory projects. The unavoidable conclusion was that they could do without him, but that he might not be able to do without them.

If you want to understand Hancock's tragedy, one way is to imagine that Richard Wilson is actually called Victor Meldrew and has nothing else but that maddeningly popular catchphrase, tightening round his personality until it squeezes the life out of him. Hancock certainly felt the constricting grip of his best-known lines; going on stage in Australia towards the end of his life, he first told the audience what he wouldn't do - "I shall not be rushing on here shouting `stone me' and `fetch him a punch up the bracket'. There will be no mention of an armful of blood." Wilson has what Hancock didn't - an identity separate from his most famous character, a life of achievement in which he is not Victor.

Early in his career Hancock made a brave move - leaving a successful radio series, Educating Archie, because he didn't want to be typecast as a puppet's sidekick. He also claimed to have been made uneasy by the sight of his wooden co-star hanging on the dressing-room door, an image which gave him nightmares. Conventionally, people are spooked by the lifelikeness of ventriloquists' dummies, by the possibility that they will assume a malign autonomy. In Hancock's case I wonder whether the terror wasn't quite different: the dread of a man who fears that without others to make words for him and animate his features, he will be left powerless.