It was a miserable night on Exmouth Market, one of London's most overhyped and over-venerated streets, especially by the foodie community. One decent restaurant and a couple of hangerson does not a Ludlow make, media chums.

We found our destination, a space that has seen off recent hopefuls The Exmouth Grill and Bar Meze in fairly rapid succession, and walked in without a reservation. There was no need; all but a couple of the tables were empty. I had e-mailed the restaurant for background info, only to be met with a deafening silence; to say we weren't expecting much is an understatement.

First glances deepened our suspicions: this is a bravely - or fool-hardily - austere set-up. In a climate where decor is afforded at least as much attention as the food (and I'm as guilty as the next chump - see my affection for the Trois Garcons lot), walking into a place as unadorned as The Ambassador gives one something of a bracing frisson. Maybe it's a reality check?

There are dark bentwood chairs and green-topped tables offering a whiff of baize; floors appear to be lino - lino! - and pale glowing lampshades whisper of the institutional refectory. There's the occasional retiring print on cream walls and, well, that's it.

Our curly-mopped waiter (who turns out to be Clive Greenhalgh, ex-Brackenbury and The Ambassador's owner) carries on the pared-down retro feel with his Pringlish Jacquard jersey. We have wandered into the 1950s. Except the food is decades better.

The menu - in a modest plastic diner sleeve, of course - is the sort of thing that brings me out in goosebumps: simple but clever dishes made from first-class ingredients. It's staunchly British in its no-nonsense approach but Continental in its brio.

I find myself in thrall to my rabbit ravioli (I'm having a bit of a rabbit moment now - must be spring). Two large, springy, silky pasta envelopes cradle a moist, subtly gamey farce of rabbit; these sit on fennel cooked in butter with a lick of caraway.

The date's chicken and foie gras terrine is good - I like the contrast between the stuffingy chicken part and the slippery luxury of the liver - but it can't hold a candle to the gorgeousness of the bunny.

Then pork belly: cooked long and slow until its fat has melted and its meat falls apart like best pulled pork - but with crackling. It comes with pillowy, squidgy gnocchi and a dark and savoury morel sauce.

Properly chickeny chicken bathes in cream-laced mushrooms and leeks with a potato gratin, a caressingly soothing dish. Only a rather gritty and stodgy cake of quince and apples dents my euphoria. Only slightly, mind you.

The open kitchen at The Ambassador, where ex-La Trompette chef Tobias Jilsmark does his thing, smells wonderful, like sweet seafood and spices and wine and caramelising meat. There's a smart wine list, with intriguing choices by the glass and the half litre; it's open all day; heck, it's even great value.

It all made me want to dissect and unpick the apparently insouciant simplicity. Aha: a main investor is Michael Belben, one of the brains behind the Eagle in Farringdon, that seminal original that spawned a million gastropubs, and a man who can genuinely claim to have helped shape the way we eat today. Seems he hasn't lost his visionary touch.

So appearances can be more than deceptive: this is one London opening that turns out to offer much more than it initially lets on. What's it an ambassador for? Being a bit less up ourselves and appreciating quality in an unassuming guise? Well, that's my best guess.