Terence Blacker: Why Sunday night's Fry-up left a greasy after-taste

What a very strange and not entirely pleasant business it must be to become a National Treasure. Some, like Sir David Attenborough or Michael Palin, might have been born for it. Others, like Billy Connolly, have had to work harder. Now and then, most recently during last weekend's profoundly embarrassing media love-in for Stephen Fry, one wishes that, for his or her own sake, the potential NT had quietly declined the honour, preferring to remain a common-or-garden, fallible celebrity.

It can be done. Ronnie Barker saw institutionalised fame heading his way, and firmly retired from public life. Spike Milligan ratcheted up his stroppiness – when Prince Charles complimented him, a sure sign of incipient NT status, Milligan referred to him as a "grovelling little bastard". Peter Cook was openly bored by the idea. Dawn French seems to have dodged it by announcing that she is going to Cornwall to die.

Unusually, Stephen Fry has been promoted to the highest level of übercelebrity at the age of 50 – indeed BBC2 cleared the entire channel on Sunday night to celebrate this important event. Coincidentally, another apparently less significant birthday, that of BBC radio, was being marked on the same night. It was, of course, presented by Stephen Fry, so that the weekend became a sort of merged celebration of enduring, old-fashioned British wonderfulness.

That, of course, is fine for the corporation but, for an individual, it must be oddly dehumanising. In an extraordinary programme of tributes (Fry must have wondered at some point whether he had died and was looking down at his own obituary from heaven), a line-up of famous people, who would seem to have nothing in common except a talent to annoy, puckered up for the great man. Kenneth Branagh, Ben Elton, Emma Thompson, Russell Brand, even Milligan's grovelling little bastard himself paid homage to Stephen's brilliance, wit, kindness, vulnerability, energy and, of course, modesty.

How could Fry allow this humiliation to happen? He is a bright and interesting man who uses his intelligence to communicate his enthusiasms. He is not a show-off or an intellectual bully, and is occasionally funny. He is an excellent quizmaster, chairs awards ceremonies with considerable charm and wit. He is a good, but not astonishing actor, director and writer.

Yet it became increasingly clear in this bizarre programme that, apart from the usual media creeps and show-offs, some normally sane people were taking their adoration for him into the realms of fantasy. Could John Sessions in all honesty have thought that Fry's novels stand comparison to anything that has been written in the past 20 years? Did Joanne Rowling really believe that criticism of Fry invariably came from reviewers and critics who were terminally, professionally jealous of him?

Here is the problem with this level of fame. It sends everyone nuts. If anyone had dared to break the general tone of adulation on Sunday night – suggesting, for example, that Fry's legendary brain is in reality an exceptional memory combined with a high level of articulacy – it would have been as shockingly inappropriate as someone farting loudly in front of the Queen.

At some point, it seems, the NT ceases to be an individual but becomes a representative of hallowed virtues. To criticise Stephen Fry now would be a vote for stupidity, for insensitivity, a vote against humour. It would be an irresponsible and unpatriotic act, like trashing Radio 4.

The sad truth is that this kind of mega-fame only happens to those who really, really want it. The reason why Stephen Fry's fiction is never truly let off the leash, why he is less effective as an actor than being himself in documentaries, is that he wants to be loved: the work is a means to an end, and that end is popularity. He can never quite forget that he is Stephen Fry.

The big birthday was marked obliquely on Fry's blog with an endearing, self-effacing, name-dropping 9,000-word essay, which reminded his readers that he is well-read, yet also in touch with popular culture, that he is both modest and really rather exceptional. Its subject, of course, was fame. His fans loved it.

Miles Kington is away