It seemed the simplest of commissions. In the end, it made me realise what Al Gore had experienced. Well, maybe not what the New Yorker called "the disappointment of a lifetime", but it was galling all the same. Summoned by the magisterial socialite Carole Stone to a debate in which I had to defend the 18th-century French artist Francois Boucher against accusations of pornography, I was delighted to accept. As long as I was joined by someone of greater art-historical standing. Step forward the NS art critic Richard Cork, who agreed to take the stand first.

The debate was held at the Wallace Collection in central London, which is currently showing the work of the man who liked tits'n'bums. I mean, the great rococo artist. There lies the problem: although Boucher had an astonishing touch, he also appears to have been partial to the sight of hanky-panky. But all in a very pleasant way, which is why Cork and I jumped at the chance to oppose the motion "Boucher: just pornography for toffs?".

At the beginning, there was a vote. And there was to be another vote at the end. The audience started off 40:20 against the motion, with roughly 30 abstentions. A stern French-art historian began, proposing that Boucher's delightful putti were quasi-paedophiliac images, and that his naked girls of 14 were little more than Loaded centrefolds. Everywhere, she said, there were pornographically proffered breasts and buttocks, the latter clearly implying that Boucher was a sodomist of the first order.

Cork and I rose to the challenge. We pointed out that Boucher was nothing other than an artist desirous of delivering sensuous pleasure to the highest degree; that his work was absolutely of the period; that he wore his learning lightly, quoting from Homer, Ovid and the Renaissance masters; and that the steamy stuff was imbued with humour. Yet it seemed our best attempts were thwarted by Alexander Sturgis of the National Gallery, who seconded the motion. He paraphrased Diderot, scorning Boucher for his "girl-on-girl" action and other misdemeanours of the brush.

The debate swept on to the floor. People rose to defend Boucher magnificently. Girls of 14 in those days were quite happy being seduced by kings or artists. Was pornography even invented in Boucher's day? Someone leapt up and talked about a film-maker called Ben Dover whose work, we were assured, was most unlike Boucher's. Someone else asked Sturgis most sincerely if he had ever been sexually aroused by a Boucher canvas. The French-art historian glared at the floor. Surely we were going to walk this.

After our closing speeches, during which I delivered (I hoped) a moving testimony from the artist - "I look only for elegance, grace and beauty, sweetness, kindness and gaiety . . . in a word, all that which breathes either flirtation or sensuality . . ." - the final vote. The result was 70:20, with four abstentions - that is, 70 people now agreed that Boucher was a mere pornographer. I wish I'd had a camera to record the smug expressions on the faces of the opposition. I turned to Cork, dismayed. Sturgis and his partner were the toast of the evening. We kept a low profile while muttering about rigged votes. Last Saturday, a phone call from Stone. "We had a recount. We got it the wrong way round!" Even at the Wallace Collection, democracy can sometimes go off the rails.