Here comes another one. Pre-Olympic London hotel opening, I mean. The eighth – hang on, no, ninth lobby into which I have wheeled my case since last spring.

Here I am, just off Sloane Street. Trotting past Ferragamo and Prada. Belgraves is the 12th Thompson hotel and the first outside North America. I remember when the first, 60 Thompson, opened in SoHo, amid the artists' lofts in 2001.

I'd have bet money on them scouting in east London for a British debut but clearly they are not pinning their colours to the Olympic mast. Belgravia is where old money and oil wealth cohabit. You won't find an emerging artist renting here.

You will find the offices of Tara Bernerd, though. London's design It girl is responsible for Belgraves' interior, having wanted, according to the hotel's own glossy magazine, to get her hands on the former Sheraton for yonks. Now she has, and she's made a masterly job of it. Restrained, cosy sophistication is marred only by trying-too-hard (or just trying) lobby art.

My room, a Double Premium, is at the lower end of the class system, the real test. It's oh so quiet, in every sense. It maximises light from an oriel window filled by a purple velvet sofa, so I can stretch out and enjoy Chesham Place, a wedge of grass with a petticoat of pink blossom.

Sexily semi-obscured by a metal bead curtain over smoked glass, a shower turns into a re-enactment of the opening sequence from Tales of the Unexpected. The loo is separated from the bedroom by two full doors. Proof that a woman has masterminded the design. A desk conceals sockets for EU and US plugs, but Wi-Fi costs a staggering £15 a day.

Down on the first floor, leather, wood and velvet, abetted by a rear wall of bookshelves, create a private club vibe, exposed brick lending a hint of New York loft. Mark's Bar (as in chef Mark Hix, who is behind the restaurant too) is clearly a new neighbourhood hotspot. I spot Trinny at one table, Charles Worthington at another.

My friend arrives. Overnighting in town and swapping a sandwich in her room for dinner with me. Who wouldn't? We settle into a crescent-scoop banquette in Hix on the ground floor. Portland crab rösti with herbs. Whipped beets with goat's curd and walnuts. Glasses of Sancerre. Beetroot is unctuous heaven, rösti is a little too thin. Grilled poussin with a tabbouleh of pomegranate and freekeh, Middle Eastern green wheat, and chargrilled rabbit with white polenta, rosemary and olives. "Rabbit, unfaultable. Slightly fewer black olives would let the polenta do its thing. Yours is absolutely delicious," says my friend, reaching over again. Of three puddings, sea buckthorn posset is the only non-success – it just tastes weird.

The Thompson group has gone haute instead of hip by picking Belgravia over Bethnal Green. Bless America for bucking a trend to prove it's hip to be square.

sally.shalam@theguardian.com, sallyshalamsbritain.co.uk