Rating: 8/10
Telephone: 020-7935 8311
Address: 34 George Street, London W1
Open: Lunch, noon-2.30pm; dinner, 6-10.45pm. Sun: 12.30-3pm; 6-10.30pm
Price: Around £120 for two, eating plenty of sashimi and sushi, including sake
No wheelchair access.

My first experience of eating Japanese was in 1979, in London, as an inspector for the Egon Ronay Guide. This particular Japanese restaurant was called Yamaju, in Beak Street. To find it we ventured up some dingy lino-covered stairs to the first floor - and promptly entered quite another world. There was not a dining table in sight, although there was a small wooden footbridge with a substantial stream running beneath it. We silently padded over the finest, chocolate-brown Wilton, discovering - yes, indeed - the bridge was carpeted, too.

No other guests were evident, though we felt almost overwhelmed by the generous allocation of impeccably polite staff who greeted us, seemingly there entirely for our benefit. All soon became clear as we were directed to a private room, paper-screened and tatami-matted, where our nine-course dinner, or kaiseki, began. We never saw another being from the outside world, yet I was told after dinner that the place had been bursting at the seams.

I was lucky enough to visit the extraordinary Yamaju once more and then - poof! - it was gone. The food had been extraordinary - I cannot begin to recall the exact details - though I will never forget my first taste there of fatty tuna and the remarkable light crunch enclosing custard-like cubes of fried bean-curd. Thankfully, it had been Egon who paid on both occasions ... I have been hooked since.

It strikes me, in fact, that if some future interference were to tell me that I might never again eat three-star Michelin, but the alternative would be the very finest Japanese cooking, I could happily live with that - I would certainly not wish it the other way around. Now only occasionally fond of the former, I always delight in the precision and simplicity of the latter. And when the man at the sushi bar at Defune tells me - expostulates, even - that I could not eat out-of-season sea urchin, it is with gently bowed head that I ask for sweet shrimp, instead. A delicious telling off.

I have been enjoying sashimi lunches at the sushi bar at Defune for, I guess, about five years, on and off. I go there most often when under the regime of a fairly rigid diet that involves eating only protein and citrus fruit. The indulgence part, of course, is the eating of impeccable pieces of very expensive raw fish. In fact, I have always thought that consuming several slivers of fatty tuna (for me, the very pinnacle of sashimi) is the closest thing to eating best beluga. It has an incessant cool richness, silky texture and, once briefly dipped into finest soy, a salty balm that seems to mimic the intense savoury quality of the caviar. And, be warned, eating Japanese is never going to be cheap; sashimi chefs are royally remunerated and compromises are rarely entertained. A serving of fatty tuna sashimi at Defune is £16 - although you could not eat two, so rich it is.

And it is the impeccable quality of sashimi here that causes me to return regularly and dig deep into my wallet. When there is, for instance, some fabulously fresh turbot - they buy fresh fish only when it is a notch up from merely spanking - they serve up this plate of about nine exceptionally thin slices with a special sauce of minced radish, spring onions and sweet vinegar that never fails to please (£14). The combination surprises and delights each time with this almost indiscernible crunch that the turbot gives to the teeth when eaten raw, as opposed to the softer yield of tuna, yellowtail, scallop or salmon in their usual soy and wasabi smearings. None the less, these are of quite fabulous quality, too, and he who wields the knife is a joy to observe as perfect slices are passed over the counter on to my traditional wooden board.

Now and then I feel the urge for just a little sushi, too. I don't know anywhere where the rice is as good as it is here: just warm and of perfect texture. Two exceptional examples are sweet shrimp sushi and rolled sushi with chopped fatty tuna and spring onion (both £9.20). The only disappointment on this visit was a lacklustre, deep-fried beancurd (£6.80). Then again, there has never been a finer one than that enjoyed all those years ago in Beak Street.