The hot news in Kennington last month, apart from black on black teenage gun crime and delays on the Northern Line, was that Cate Blanchett and Judi Dench had been spotted having lunch together in the local branch of Pizza Express. Now, this tells us nothing more about the folksiness of English (OK, and Commonwealth) actresses than we knew already: Emma Thompson keeps her Oscar in the loo, Rachel Weisz drives a C-reg Jag and Helena Bonham Carter hasn't brushed her hair since 1983 (and that was for a part) — British lady actors are so determinedly nose-picky and sock-holey you absolutely expect them to be sitting in Pizza Express whenever you walk past, dressed in old bin bags and paying in coins. Indeed, how surprised would you be, honestly, to see Dame Judi in a pair of giant trainers rummaging in a wheelie bin for her lunch?

Nor does it tell us anything about the Kennington Pizza Express that I didn't already know from popping in occasionally to get a pizza for my girlfriend when all she wants to do is sit in bed watching This Life on DVD and chain-gobbling capricciosas. There is nothing special about it. It is as crapola as you'd expect, serving the doughy, overly sweet pizzas at eye-popping mark-ups that you know and love. I pay for extra cheese (I've given up trying to pay for better cheese) so that it's not just spotted on like acne, and for extra olives (the days of asking "Could you chuck on a few extra olives, please?" have long gone) and I ask them to cook it five minutes longer than usual to allow at least some of the glutens in the base's floury gack to be rendered digestible — but they pay no attention, hand the order slip to the pizzaiolo (ha!) and go back to gibbering in Polish and ignoring the seated customers.

So I think what it tells us most about is Kennington. And what it tells us is that, despite the lovely Georgian squares, the proximity of Town, the excellent transport links and the home of my favourite person in the world, there is not much going on gastronomically. For Cate and Judi are ladies who, one would have thought, would not support grismal mega-chains resting on ancient, creased, properly foetid laurels unless they really had to.

If they'd asked me for advice I might have pointed them, I suppose, in the direction of the White Hart, for good chips, a pint and a squiz at the footy on the big screen, or to Amici, which is undoubtedly the best Iranian-run Italian in London, although it has a clientele so gay that two famous actresses walking in might have been more than the place could bear. Cate and Judi have both played Elizabeth I in big productions and have probably had enough of moustachioed couples looking at them over their lorgnettes and saying, "and I thought we looked a right pair of queens!" Or, better still, they could have hopped four stops on the Tube to Trinity, where I went the other day and had, well, I have to say, as close to an absolutely perfect experience of eating out as it is possible to have.

Having established that Adam Byatt, formerly chef at Thyme in Clapham (who took the enterprise to Covent Garden, renamed it, reshaped it and eventually washed his hands of it) was back in Clapham and cooking brilliantly again, and that Rachel was free for dinner, I had managed to secure a table, albeit a late-ish one, and thus spent all day in my favourite possible state: looking forward to dinner with the woman I love in an exceptional local restaurant. If only all my days were like that. Oh, they are.

Clapham was cold and crisp and quiet (mostly because Operation Trident has recently moved down here in force) and the restaurant was just right: nice size, low lights, full but not shouty, and the waiter, when I asked for water, said, "Tap?" Rachel laughed.

"What's so funny?" I asked.

"That's the first time we have ever been offered tap water," she said. "You don't think it's a bit of a coincidence?" "No," I said, full of high dudgeon. "It just means my anti-bottled campaign has changed the way restaurants offer water." "It means it's changed the way they offer water to you," she said. "There's no way they haven't spotted you." I refused to believe her, and still do. I used a false name, it was dark, Rachel did the ordering — I swear, they had no idea. It is a Brave New World I have made, and it drinks tap water.

It also eats extremely well. Starters were fine, not mind-blowing, but I like it that way — I hate a meal that starts with a fanfare and tails off. I had five oysters (an odd number, literally) that were poached and served in a champagne velouté with sweet-cured cucumbers. They reminded me of something Marco Pierre White used to do (in the kitchen, obviously) and the dill-scented vegetable slivers had the effect of making these most unkosher of shell-dwellers taste faintly Jewish (in a good way, in a good way).

Rachel had a huge raviolo of crab and tarragon and said it was like giant dim sum, but she just meant that it was a dumpling and she liked it — I didn't give her the full "in the Cantonese language, 'dim sum' mean little bites of happiness" lecture.

Before the main courses, we were brought bonsai portions of a dish we had not ordered but should have done, and will again, for the rest of our lives, and then after we're dead, when they serve it in Heaven, accompanied by harp music. (I insisted to the chortling Rachel that it was quite possible everyone receives the free extras, but felt I was losing the argument.) It was just a claret-coloured slice of saddle of Orkney lamb, but, oh, my Lord. Rich and textured like tongue, deep and grained like beef, high and round like venison, with sweet, aromatic fat like mutton. And a little slice of turnip tatin, just to give it a tiny nip to keep its feet on the ground.

Just, just, just, oh.

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