It was at the urinals that David Hockney found himself next to the prime minister. As one of Britain’s most celebrated living artists Hockney was attending Labour’s conference last week, fuming against the government’s proposed public smoking ban. So he turned to Blair and said: “You missed my speech.”

The prime minister, Hockney reports, flashed him one of those cheesy grins that suggest he hasn’t the foggiest who Hockney is. Still, since Blair told Ian McEwan that he was a keen collector of the novelist’s paintings, perhaps our man should be grateful that the PM didn’t announce he was a huge fan of Hockney’s novels.

Here, at least, was one protesting delegate even Labour dared not eject.

But it dearly would have loved to, for last week Hockney created a bigger splash than most of the cabinet. He had us spluttering with delight when he took to the airwaves to bellow at Julie Morgan, a nannyish Labour MP: “I think you are too bossy, chum. You are dreary, absolutely dreary.”

Which indeed she was, but she had probably sailed through life without anyone informing her of this essential truth on the Today programme. Hockney is in that blissful position of feeling free to say whatever he likes, a combination of Californian confidence and old Yorkshire bluntness.

Uh-oh. I discover the Brighton restaurant where I am to dine with him bans smoking. Hockney smoulders in, wearing grey chalk stripes with a pink rose and a badge he designed declaring “End Bossiness Soon”. And the first thing he does is light a cigar thicker than John Prescott. A waitress bustles over, but Hockney clamps his beady eyes on her through the smoke and she retreats, sharpish.

“They say smoking is bad for you but they used to say the same about w******,” the increasingly deaf Hockney booms across a room of dating couples. “Even if it was, you can always wear glasses.”

There is more than a hint of the naughty schoolboy in Hockney. With his thin red tie and full, clipped hair he looks eight in the flesh, not 68. I ask how many fags he smokes and he replies: “Ten a day — and 20 at night.”

The restaurant is grander than it is good, so when the waitress asks Hockney how he would like his lamb he adopts a Yorkshire accent thicker than homemade gravy: “Ooh, just right please, pet.”

The waitress probably goes to the kitchen declaring they have a right chump in tonight, not realising she has just spoken to a great Englishman who redefined what it is to be cool.

Hockney, I suspect, enjoys having a good old stir. He says of Blair’s failure to recognise him: “I don’t think he has many aesthetic interests.” And he lays into the prime minister for insulting the memory of the Queen Mother by tipping up at her funeral in a lounge suit, “as if she had been Mrs Adolf Hitler”.

Warming to the PM-bashing theme, he says of Bob Geldof and Bono: “A couple of Irish minstrels give a concert in Hyde Park and Tony Blair jumps to it, but millions march against a hunting ban and he ignores them.”

Back to tobacco. “I have just read a biography of Mao: he was a smoker and an intellectual,” he says, expounding his theory that all the best people smoke. “Hitler didn’t smoke. Mind you, he was a painter. Still, in the Thirties they would not believe we would regard the merchants of death as tobacco manufacturers. Ken Clarke is treated like a virtual murderer, and all he does is make cigarettes. I am far more worried about the arms manufacturers who go into No 10.”