Mash is a smash, though some things are not as they should be. By Ben Rogers
Halfway through our dinner at the Mash bar and restaurant, Mash's owner, Oliver Peyton, came up and introduced himself. "You must," he said, "be a restaurant reviewer." I don't, in fact, usually take notes until the end of a meal, and even then only if I am vaguely sober, but there was so much going on at Mash I was scribbling from the moment we arrived. And there, perhaps, lies a problem.

The 1970s are back with a vengeance, and Mash's main inspiration is provided by that decade. Of course, there were many 1970s, and Peyton's much-publicised Great Portland St emporium has taken its cue not from the era of Hair, tie-dye and home-made bread, but from its more glamorous, richer, futuristic counterpart. Mash gives us a taste of yesterday's vision of tomorrow: it looks like a set from Sleeper. What this means in concrete - or rather in fibreglass and Styrofoam - is organic forms, hexagonal floor tiles, dens and built-in furniture, Hush Puppies and kipperish ties, tulip-shaped champagne buckets, lavender, pea green and peach tones, and wildly coloured cocktails.

If Mash was just this, it would be a funny, stylish and above all voguish exercise - a trip back to the future. The problem is that Peyton is overflowing with ideas and hasn't been able to resist using a lot of them here. The loos, all steel and mirror, the black-clad waitresses, the knowing art, the gleaming micro-brewery, all speak not of the Seventies but of other decades.

And it's not just in appearance that Mash sends out mixed messages. It's not clear the place knows what it is: spread over two floors, and open 18 hours a day, it functions as a restaurant, a bar, a deli, a diner and a cafe. You can drink specially created cocktails, or sample the fruits of Mash's "open brewing philosophy" in the form of four or five different types of home-brewed beer. The wine list is, of course, cosmopolitan, but the restaurant also offers healthy Japanese-style juices, full of royal jelly, ginseng, honey and ginger. At the end of a meal you can drink grappa or a giddy choice of teas. The two incongruously middle-aged men on one side of us broke into a bottle of Hennessy, the table of women on the other side went for a pot of Jamaican Blend tea, "roasted chicory roots, cinnamon, cardamom, ginger and black peppercorn".

The food, too, goes off in a dozen directions at once. If an appetiser of wood-roasted vegetables is up-to-the-minute, the pizzas on offer seemed oh-so-terribly Eighties. The smoke swirling around our table felt perhaps Sixties, the buttermilk pancakes and maple syrup, Fifties. In retrospect, the erratic service was quintessentially Forties.

After having being open less than a week, the kitchen was still, one waiter explained, "settling down". On the night we ate at Mash the head chef was absent, and executive chef Bruno Loubet was manning the stoves. "He is not," Peyton sighed, "very pleased about it." Nor, evidently, was Peyton himself: "I know I should not say this, but we have not got the food right at all."

If this was a ploy to make us sympathise, it worked. The food really was all right. But the bread, olive oil and roasted garlic we ordered never arrived, and air-dried Cheshire ham came wrapped around bread sticks, which did nothing for it. But the ham worked well with sweet pickled fig and onions, and a generous mound of tuna tartar served, Nobu-fashion, with lime, sesame, mint and soya, tasted deliciously fresh. The pizzas, too, were thin and tender, and their toppings - one of aubergine puree, fennel and Parmesan, and another of mozzarella, pesto and rocket - promised well, though delivered less. A neck fillet of lamb arrived pink and flavoursome and an accompanying confection of preserved lemons and capers added a successful twist. Desserts, basil and mascarpone ice-cream with stewed rhubarb and a huge helping of the Indian ice-cream, Kulfi, scored high on exoticism, although the first was bland, and the second almost too spicy.

Aside from the food, there are some beautiful things here - especially, the flinty curving stone staircase that leads up to the first floor - and, eating here, both floors packed to overflowing, London never felt richer or hipper. Yet Mash itself, if you stay off cocktails and digestifs, is relatively cheap. Our hefty meal for two with a glass of wine, a pint of wheat beer and coffee came to pounds 58 without service. One point though. Chatting to Peyton as we were leaving, we asked him, above the Boogie Nights soundtrack, whether he would be putting in more tables. "No, I don't like it when you can hear what people at a neighbouring table are saying." Well, yes, but it would be good sometimes to hear what those nearer by have to say. Your days as a nightclub owner are over, Oliver. Turn that music down

Mash, 19-21 Great Portland Street, London W1 (0171-637 5555). Open breakfast, lunch and dinner, 7 days a week. All major cards accepted