Any social historian flailing about for a thesis designed to illustrate changing priorities in Britain either side of the millennium is welcome to this: From Public Service To Private Dining: How The Restaurant Industry Ate The Leftovers Of The Postwar Public Service Ethos. Over the past decade, I've eaten in buildings that used to be town halls, cottage hospitals, fire stations, police stations and, somehow most depressingly, libraries (not to mention countless banks). But until a trip to Surrey, I'd somehow avoided eating, knowingly at least, in an erstwhile post office.

If Tony Tobin, the TV cook who is chef-proprietor of this vast space, had respect for tradition, those ringing to book would be made to wait 27 minutes in a telephonic queue before being informed, "Receptionist number seven, please." Instead, a recorded message warns of a long hiatus due to extreme levels of interest in his cunningly named Post, and 2.37 seconds later a human being comes on to the line to offer a choice between "brasserie or fine dining", take the details and finally say, "What we'll need to do to confirm is take a credit card number." A braver soul would have replied, "Look, mate, it's Banstead high street, not Claridge's, so you can lump the Ramsay showboating for starters."

Perhaps this credit card cobblers is what might once have been known on this site as part and parcel of the modern restaurant game, but it seemed even more pretentious when we reached this tripartite operation, passing a gorgeous deli and a vast, airy all-day brasserie before ascending to "fine dining" to find only one table occupied by a Rotarian quartet. It was doubtless in this determinedly 70s room (brown-and-cream colour scheme, offering melancholic views over redbrick houses) that post office staff used to go through the mail checking for treasury notes to sequester. Tobin seems less willing to thieve from his punters, given the quality of ingredients, though that said, a meal costing a little over £40 is hardly a steal in the provinces. We could argue for hours about the implications of the phrase, but what we could all agree about "fine dining" is that it has nothing to do with stale bread. Here, the various fancy-dan concoctions, including brie and grape, would have been rejected out of hand, or beak, by any self-respecting duck.

What followed was highly curious, as technically outstanding cooking was repeatedly ruined by the same mistake. So over-sweetened was every dish that we began to wonder if Tobin had been misinformed that we were Type 1 diabetics on the verge of hypoglycaemic shock. Chilled yellow gazpacho with chunks of crayfish and lemon oil was "fresh-tasting and lively, but cloyingly sweet", said my wife. Quick-fried salt and pepper squid had decent texture, and came with a zingily delicious salad of peppers with coriander, but the vinaigrette was twice as sugary as the gazpacho.

The main courses offered more of the same confusion. Cubes of pan-fried duck breast were beautifully cooked to juicy pinkness, and looked handsome beside potato rösti and a flower-shaped parsnip tatin, but the orange sauce that came with them might have been a reduction of molasses. As for my wife's fillet of sea bass, this, too, was cooked to perfection, but the aftertaste of the thick, potent onion soup with which it came made Pepsi seem like grapefruit juice.

"The infuriating thing is that the guy's obviously very talented," my wife said, palpably auditioning for my job over paradoxically unsweet puds ("Topsy Turvy" plum tart with honey ice cream was sensational). "It's really clever how he layers all the flavours so you get them one by one, a bit like the chewing gum in Charlie And The Chocolate Factory. But the overpowering sweetness, well, it's just weird."

So it was. And so, come to that, is the presence of such a swanky, ambitious project nestling among the usual high street chains in commuter-belt Surrey as if mischievously misdirected from a central London destination by a vengeful postal worker put out of a job.

Rating 5/10

Telephone 01737 373839

Address 28 High Street, Banstead, Surrey

Open all week, lunch, noon-2pm (3pm Sun; closed Sat), dinner, 7.30-10pm

Price Various set menus, from £16 for two courses, £21.50 for three, up to £52 tasting menu