Nobody could accuse Sir Terence of being crude, but his legacy of anorexic good taste may be a more dangerous enemy of exciting design
A nation rejoices. SIR Terence Conran is 70. Let there be parties; let there be fireworks. The great man celebrates himself with a splendid pyrotechnic jamboree in his fiefdom of Conranopolis (formerly trading as the Pool of London). The sky is lit in his honour.

Yet this is also an act to delight the common people, an act of noblesse oblige for which this common person, watching from my terrace 800 m away, was grateful. It was a brief (but not that brief) chromatic interruption of London's perennial dullness. It was, too, a metaphorical summation of Conran's gift – which is to give the common people what he wants, in the hope that what he wants is what they'll want, once they've learned to want it because he wants it – and he knows how to make them want it without their realising. Snake oil salesman? And then some.

He does, however, occasionally get it wrong. Take his ingenious method of composing "a sort of autobiography". You get your publisher to telephone or email 150 acquaintances and solicit questions from them to Mr Conran. It's an idea that belongs to the laziest end of literary modernism, where the subject of the interviews is always taken on their own terms and allowed to decree a sort of manifesto for their work. It might have come off, had the other 149 people wondered, as I did: "Given the choice between John Redwood and Ann Widdecombe, which would you have intimate relations with, and why? You're not allowed to say neither."

In his introduction, Conran describes that question as "incredibly crude" – which is apt – and from thence makes an unconscionable leap into calling me, in the dramatis personae of "his" book, "crude … from the Murdoch manger".

But we pay for civility by neglecting risk. There is no longer room for oddities and prodigies

Look: I have no problem with being described as crude. After all, my last column in this space was a hymn to Southampton, native city and cultural wetnurse of Benny Hill and Ken Russell: can you get cruder? Well, yes, you can. Getting called crude by Conran is some sort of counter-indicational laudation. Craft will always call art crude. Craft is the very obverse of art. Good taste – of which craft is the militant arm – is the enemy of art: Conran seems bemused by art, by its awkwardness and by the bolshiness of those who practice it. Still, it's better that we have good "bad taste" rather than bad "good taste".

And this is something Conran must be genuinely thanked for: he has propagated douce, user-friendly modernism; he has turned our heads; he has made the abnormal normal. But he diminishes himself by importuning clowns such as John Birt to flatter him thus: "You may recall, as I do with pleasure, your excitement at seeing furniture that you had personally designed in my office at the BBC." Don't you love that "personally"? I think we can see now why Birt was so exercised by the scrupulous resolution of Paxman and Humphrys. Boasting is an all too human trait. It is best done personally. Getting others to do it for you is rather squalid.

Conran's legacy is not of his own devising. He is a facilitator rather than a creator. This is something that he is loath to admit: he is the producer who wants to be the director. His achievement has been considerable, but it is not the one he is willing to admit to. One of the reasons that British building and design has attained its standard of high competence these past 10 or 15 years is that it has borrowed a singularly Conranian tendency. It has eschewed originality and eccentricity. It has worked from a de facto rulebook whose primary author has been Tel himself. His example, and that of Lord Foster, is everywhere apparent. Sleekness, cleanness, austerity – these are the new norms.