Our little group was shocked by Charlotte's coke-fuelled nights of sex with greasy Les

Charlotte has let us down. For more than ten years, she and "Mickey Boy" have been the very model of a modern marriage. From time to time we've been privy to their minor disagreements, but these were always handled with such good humour that not one of us imagined that they constituted any threat to their happy togetherness.

The term is now hideously out of fashion, but it would be fair to describe Charlotte and Michael as role models. "They're so respectful of each other's opinions," Geoff would say with an explicit reference to his own partner's militant vegetarianism. "What I like about them," Anna would say with a nod towards Gordon's predilection for silly jokes about dyslexics, "is their wonderfully compatible sense of humour."

But last Saturday night, as we sat around at Sally's savouring a splendid Jamie Oliver meal of seared scallops and smashed white beans, the bombshell dropped. Geoff's partner, Marie, reported an extraordinary conversation that she'd had at a recent book launch with her old friend Estelle. In the course of swapping mutual acquaintances, they'd both come to rest on Charlotte. But even as Marie was embarking on her usual trope about the enduring miracle of her relationship with Mickey Boy, Estelle casually announced that she was less concerned about Charlotte's emotional state than about the gap between her nostrils. "Did you see those appalling pictures of that woman with no septum? The one who snorted six grams of coke a day? That will be Charlotte in a year if she doesn't knock off the nose candy."

Marie knew that, for the sake of us all, she had to press on. "I didn't know Charlotte took a lot of coke."

"Oh yes. She loves the stuff. She told me once that it meant you had to wait much longer for a decent orgasm, but when it came it went right through you like an electric shock."

"Isn't Mickey Boy worried about her habit?"

"Mickey Boy? I don't know about any Mickey Boy, but I should think it goes down well with big Les, that greasy despatch rider from Metro Express she's been knocking off for the past six months."

After Marie had unloaded her sensational news on Saturday, there was a terrible silence. No one felt quite able to look up from the strawberries and balsamic vinegar. Our god had failed. Geoff was the first to react. "I thought only the other night that her voice was becoming terribly nasal. As though she had permanent hay fever."

Miles was even more frank. "I always reckoned there was something a bit dirty underneath all that sweetness and light. Like with Julie Andrews and Doris Day."

We sat around until after midnight debating some of the other finer issues. Had Charlotte deliberately cultivated our company because it gave an extra frisson to her drug-fuelled nights of sex with the man from Metro Express? Should we now acknowledge that there was no such thing as a perfect relationship and proceed to celebrate our own flawed partnerships? What on earth was it like to have an orgasm that went right through one like an electric shock? And what were we going to do about Anna's summer party? Should we invite Charlotte and Michael as usual?

It is, I think, indicative of the liberality of our little group that we decided Charlotte should receive her usual invitation - even if it was, to my mind, marginally undermined by Anna's proposal (carried by five to three) that Michael's place should, at least on this occasion, be taken by greasy Les.