The Diamond Jubilee Tea Salon at Fortnum & Mason, 181 Piccadilly, London W1

The Diamond Jubilee Tea Salon is decorated in Fortnum's familiar duck-egg blue

High tea – there's a thoroughly English concept. Not quite tea and not quite supper, a collision of sweet and savoury flavours, a repast based on "the cup that cheers but does not intoxicate" but with the possibility that the tea will be laced with rum.

It was well established by the mid-19th century, and was more associated with the north than the south of England. Arnold Bennett, in one of his Staffordshire 'Five Towns' novels, describes "a high tea of the last richness and excellence, exquisitely gracious to the palate, but ruthless in its demands on the stomach ... hot pikelets, hot crumpets, hot toast, sardines with tomatoes, raisin bread, currant bread, seed cake, lettuce, homemade marmalade and homemade hams...". It's cognate with the 'tea' that working-class labourers wolfed down on coming home from work – though when it was introduced to the Home Counties, the savoury components became more delicate than their northern equivalents.

Fortnum's, the Queen's grocer's shop, has been dishing out tea to paying customers since 1707 and has turned the afternoon ritual into a posh and pricey business. The fourth floor, fine-dining area, christened the St James Restaurant when it opened in 1957 (F&M's 250th anniversary) was tarted up for this year's royal celebrations, renamed the Diamond Jubilee Tea Salon, and opened by Her Maj in March.

This newspaper has long turned a sceptical, if not quite sour, face to the pointless celebration of monarchical trivia (births, weddings, funerals) but you can't walk into the Fortnum's tea salon without feeling a teeny bit regal yourself. The reception desk stands before a display of the shop's celebrated tea caddies, great fat canisters of Pekoe and Darjeeling as imposing as guardsmen. The salon is a dog-leg, stretching away to the right, curling round to your left where the cakes are (and whither you naturally gravitate).

The décor and crockery are that familiar Fortnum's duck-egg blue, but associated shades of turquoise and pale green make the carpet and upholstery shimmer. The wood trim, like the napery, is a dense, wedding-cake white. The cake trolley is a beautiful silver object with a marble top. You sit at your table – the tables are set luxuriantly far apart – and regard the huge globes of pink peonies in their silver table-vases and the noble spires of the Royal Academy visible through the window and think, ah yes, I was born for this life...

But you weren't. You're here to address the food. The hilariously pricey High Tea menu starts with a choice of familiar savouries: cheese and onion pie, cheddar soufflé, lobster omelette Victoria, eggs Benedict, Welsh rarebit. They're small helpings, and almost perfectly judged. My baked duck egg could have been more set, but the sautéed mushrooms and Jersey royals had been cooked together until they formed a buttery emulsion that welcomed the golden yolk like a friend. Angie's smoked salmon, served on a blini with crème fraîche and Aquitaine caviar, was a touch of fishy heaven underscored by chopped chives.

To be honest, my savoury dish left me positively aching for a meaty main course and it felt just wrong when our charming waiter brought the cake stand. Victor, who's over here from Romania, doing a postgraduate degree, had talked me into taking a glass of Sancerre with the first course, and it seemed a terrible comedown to switch to tea.

But the Ladurée macaroons were so chewy, the scones so softly pliant under their dressing of Fortnum lemon curd or Jubilee Royal Sovereign strawberry jam and cream, the Jubilee Blend tea (a hybrid of India, China and, how quaint, 'Ceylon') so light and smoky, that I stopped whingeing and yielded to this orgy of multi-level sweetness.

Like the triple-decker plate stand, they offer you three levels of cake: macaroons, then a plate of tiny single mouthfuls – rosewater éclair, dark chocolate tart, raspberry and peach melba parfait, a stunning pistachio and cherry millefeuille using slivers of sponge rather than pastry. When you can't take any more, they steer you to the trolley, to choose one slice each of the serious cakes: a Bakewell tart, a Sachertorte, a Battenburg and an angel cake. They're all made fresh each morning by Jane Smith, who deserves a medal for keeping alive the idea of cakey perfection, miles removed from Mr Kipling. The angel cake – an indefinably sexy gateau with dirty-pink icing like bruised raspberries – was densely layered but light as a breeze, and probably the best cake I've eaten since childhood.

I'm no sucker for posh dining. I'm not someone to be taken in by dreams of aristocratic luxury or the paraphernalia of sugar tongs and tea strainer. But I loved the Fortnum's experience. It recalled a long-lost dream of the perfect tea room where your mother once took you, and told you to behave nicely. If you can stand the idiocy of spending £80 for two, I suspect you'll love it too.

The Diamond Jubilee Tea Salon at Fortnum & Mason, 181 Piccadilly, London W1 (0845 602 5694). £40 per head, including tea.

Food ****
Ambience *****
Service ****

Tipping policy: "Service charge is 12.5 per cent discretionary, of which 100 per cent goes to the staff; all tips go to the staff"

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This 1826 institution serves fine Scottish oysters – try them Rockefeller style (with spinach and mornay sauce) or simply as they come.

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