How's this little lot grab you? Couscous-stuffed lamb shoulder on chard and white beans. New potatoes in parchment with rosemary, garlic and bay. Braised carrots and turnips. Broad beans, french beans and sugar snaps with mint. Beetroot, red onion, lentil and feta. Mixed leaf salad with cherry tomatoes and courgettes. Salivating yet?

Now what if I was to add that all of those dishes - and I really do mean all of them - made up half of a two-course set lunch that cost all of £13 a head? And that everything was organic and as local as you could wish for? And that the setting was an idyllic valley in the heart of Devon? There has to be a catch, right?

And there is, but only a little one - the place's licence means that, before you can tuck in, you have to do a tour of the farm to which the restaurant is attached. But if you think that means being dragged around muddy fields, stepping in God knows what while some bumpkin tells you that vegetables grow in the ground, think again. For one thing, the farm is Riverford Farm, purveyors of organic veg since the late-80s, way before they became fashion accessories. For another, our tour guide was Guy Watson, the brains behind Riverford's organic transformation and a man so full of beans (literally, in all likelihood, as well as figuratively) the Soil Association should hire him as a mascot.

Watson loaded the day's lunchers on a tractor trailer (our group was 50:50 adults and children, but it was hard to tell who was more excited), then took us round his plot, stopping here and there to show off various parts of the operation and let us fill our boots with whatever took our fancy - in my case, a big bagful of basil, a few kilos of tomatoes, a punnet of strawberries and a kohlrabi or four. Well, it's not often you get a free doggy bag before eating.

With that it was time for lunch in a converted barn, all bare wood and glass, with a collection of eight-seater trestle tables in the middle, an open kitchen at one end and a box of kids' toys at the other. So far, so basic. It's a communal dining space, so you're obliged to sit with strangers - yup, the very thought usually makes me groan, too, but somehow here it made sense. And while the room relaxed, head chef Jane Baxter and team got busy trying to feed 60-plus diners all at once. Baxter's got good form, too, having cut her teeth at Joyce Molyneux's Carved Angel, before a stint at the River Cafe and a round-the-world cook's tour.

Then they brought to each table a big white plate spilling over with meat and five bowls brimming with the vegetable side dishes. "Blimey," gawped my lunch date. "It looks bloody fantastic." And it was, with bells on. Every single dish was simply wonderful, not to mention wonderfully simple. From the first sweet bite of beetroot to the last forkful of irresistibly toothsome lamb with gently spiced stuffing, this was a meal that was testament to the fact that many of the raw ingredients had still been in the ground that morning, as well as to the kitchen's skills at knowing when to leave fabulous produce well alone. There was so much food, though, we treated the spread as two separate courses: a meze-style vegetable extravaganza of such concentrated, pure flavour it would convert even Ronald McDonald, followed by the meat, spuds and salad.

All this we washed down with a plucky, £16 bottle of Sharpham Red from just down the river Dart - it seemed churlish not to stay local on the booze front, too - and then we were summoned to the counter for pudding. Any of these take your fancy? Plum crumble. Sticky toffee pudding. Apricot and almond tart. Strawberry pavlova. Strawberry tart. Mango pavlova (the local provenance mantra going way off-message there). Chocolate cake. Custard and cream optional. It's not often you come across such a selection of proper puds, properly done, so it was torture choosing just one. "You can always come back for more," said the woman at the counter, sensing our distress. So we did. Twice.

They saved the only duff note until last - an insipid imposter of a coffee at £1.65 a cup - but even that couldn't spoil a memorable dining experience. It's a kitchen in a field, yes - but it's so much more besides.

Rating 9/10

Telephone 01803 762074.

Address Wash Barn, Buckfastleigh, Devon.

Open April-October, lunch and dinner (all diners must do a farm tour). Price £20-25 a head all in.

· Matthew Norman is away.