Belgravia's Mango Tree claims to offer genuine Thai dining - which apparently means rushing you through your courses while the staff pack up around you

Post-theatre dining may be easy to come by in London's West End, but just try finding a table in Victoria after 10pm. Thrilled by the magical production of Kiss Me Kate at the Victoria Palace, we craved a restaurant with a bit of razzmatazz and Broadway glamour; a pizza just wasn't going to hit the spot. So we were pleased to alight on a brand new, and very glamorous, Thai restaurant near the theatre, where scruffy Victoria yields to toney Belgravia. Perhaps The King and I would have been a more suitable appetiser for a Thai banquet. But Mango Tree was within floating distance, and, crucially, was prepared to take a 10.30pm booking.

Mango Tree promises an authentic Thai dining experience, because it belongs to a Thai-owned restaurant group; in fact, it's the sister restaurant of a successful original in Bangkok. Before the London opening, the premises received an official Buddhist blessing, and the press release says the restaurant is designed "in the feng shui style" – a bit like describing food as cooked "in the organic style".

But it's authentic only in that it has all the atmosphere of an international luxury hotel in Bangkok. The first thing we noticed on entering the lofty, minimalist dining room was a number of incongruous and ugly Christmas decorations (and this in early November). Maybe the Thai owners thought they were paying due deference to local custom by titivating their expensive designer décor with tinsel and dwarf silvery Christmas trees. But the result looked like a Conran shop window display customised by a Generation Game contestant.

Though it was late, the other tables were occupied, mainly by business types. Some of them were perched uncomfortably on benches whose ultra-wide cushions forced them to choose between slumping so their heads were at table-height, or sitting up straight with their feet sticking out, toddler-style.

We'd arrived on time for our booking, but were still hurried through each stage of ordering, with discreet prompts that the bar and kitchen were about to close. Consequently, we weren't able to do justice to the lengthy menu – a sturdy, laminated item illustrated with pictures of selected dishes, in a distinctly un-Belgravian touch – and panicked into some fairly conventional choices. A pity, as Mango Tree serves a wider than usual range of regional food, including spicy dishes from the south of Thailand, such as yellow curry made with whole poussin and new potato.

To start, a cold salad of raw grated papaya dressed with lime juice was a pleasantly sharp companion to breadcrumbed prawn cakes, each stuffed with about six succulent prawn tails. Of our main courses, green chicken curry was made with corn-fed breast meat, the gravy richly spiced but not so much that we needed to reprise a chorus of "Too Darn Hot". Stir-fried Chinese kale provided roughage, but not much in the way of flavour, and a thin omelette spiked with shallot, onion and parsley was, well, an omelette. And phad thai – the country's most famous noodle dish – was remarkable only for the price, an incredible £15.50. OK, so it contained more prawns than you'd get from your average takeaway, and a carapace of omelette webbing, but it would have had to park my car to make it worth 15 quid.

Having begun cleaning up around us, only stopping short of mopping the designer concrete floor, the waiting staff started to go off-duty. A procession of shantung-clad exquisites filed into the kitchen, to emerge moments later bundled up in anoraks and bobble hats. It was like staying too long in the theatre and glimpsing the wigless principals trudging from the stage door to the bus stop.

Desserts were off, our waitress apologised; "Chef's gone home." At this rate we would be left with just the night watchman for company. "You'd think a restaurant called Mango Tree would be able to rustle up some fresh mango," harrumphed my disgruntled dinner guest. But a friendly manager saved the day by snaffling us some coconut ice cream from the deserted kitchen.

With a pot of green tea for two priced at a staggering £6.50, it was hardly surprising that the bill climbed to £40 a head, including a couple of Tiger beers each. Still, it's an expensive area, and there are some good things about Mango Tree, chief among them the lovely, friendly staff. The food may be little better than you'd get in your local high-street Thai, but this is no ordinary local high street; the restaurant sits opposite the garden walls of Buckingham Palace. Should one of the Windsors decide to pop in for a bite, however, they'd be well-advised not to arrive after 10pm. E

Mango Tree, 46 Grosvenor Place, London SW1 (020-7823 1888). 12pm-2.45pm (not Saturday) 6pm-10.45pm. Disabled access.