The new Claridge’s Restaurant needed to be visited at some point, because the hotel is a London institution. Always the same but, oddly, always evolving, too – I’ve been treating myself here for at least 25 years. Claridge’s is the doyenne of classy, pricey metropolitan hotels. It is Audrey Hepburn eating a caviar blini while wearing a tiara, with crunchily expensive carpets, top-hatted doormen and a delightful art deco ladies’ bathroom. Post-pee, an attendant beckons you to a mirrored dressing table to powder your nose.

All this bling remains constant, but in other ways Claridge’s isn’t afraid to change, particularly in its main dining room, where in recent years it’s said hello and goodbye to Simon Rogan’s esoteric food journey at Fera, followed by a warm embrace for Daniel Humm’s Davies and Brook, a sibling to New York’s Eleven Madison Park, although he, too, packed his cases pretty quickly. Creative differences, they said: Humm wanted to turn the whole menu vegan, and Claridge’s didn’t share his vision for multiple courses of petals, fauna and parsnip shavings.

So what for Claridge’s Restaurant now? Well, something rather revolutionary, actually: it has been reborn as a straightforward restaurant with a low-key chef and serves breakfast, lunch and dinner. Claridge’s describes itself as British, and the short new menu is full of unchallenging yet pleasing terms such as steak au poivre, baked alaska, chocolate souffle tart and roasted Norfolk chicken. It’s not pommes puree, it’s mashed potatoes, and no one has deconstructed that chocolate tart either. The most challenging offering to a picky eater is the beef tartare with a confit egg yolk and bone marrow.

Starters such as black truffle crumpets and goat’s cheese and pear salad are clearly marked as the “first course”. With its sheer simplicity, the new restaurant’s identity is spelled out in all the things it doesn’t do: it doesn’t have a pretentious one-word name, it doesn’t make you guess what the dishes actually are by listing only their component ingredients, it doesn’t proffer a vertical list of 20 sharing plates at various prices and make you work out what might make a proper dinner, nor does it keep you there for so long, while forcing you to eat 16 courses, that you feel imprisoned.

No, here you’re whisked back in time and across the mosaic floor while savouring art deco flourishes and fabulous pendant lamps. Coo at the Calacatta violet marble and the antique brass, perch your bottom on a leather banquette, then order a leek and watercress velouté with a mini parker house loaf that comes with a small pat of Claridge’s embossed butter, because of course it does – it’s Claridge’s. If you want to ooh and ah over a menu, go to Ikoyi or Mountain; queue in the rain for a Supernova burger or for Mystic Burek. The capital is teeming with groundbreaking, puzzling, horizon-expanding dining experiences right now, but none of them is happening in here.

Instead, Claridge’s is a jocund, elegant time over a plateau de fruits de mer that features a feast of fine de claire oysters, fat langoustines, crab, clams, mussels and scallops. It’s £45 for one person, and for another £30 you can add half a lobster. They’ll bring an assortment of prodding, scooping and cracking devices, which will feel oddly formal, but, importantly, they will pretend not to notice if you don’t use the correct ones in the right order. The seafood is beautifully dressed and, with such a small menu and rapid turnover, notably perky and fresh.

In the event of another world war breaking out, some people say they’d head for the kitchen department at John Lewis and live out their final hours fondling Le Creuset ramekins, not least because it is the ultimate safe space. I agree with the sentiment, but all things considered I think I’d now go to Claridge’s Restaurant, after first spending a penny in London’s loveliest lavs, handing my coat to the wonderful reception staff, accepting the pretty token they’d give me in return, before settling down with a bowl of pumpkin agnolotti – a hearty, sunset-shaded bowl of fresh pasta with chunks of baked delica pumpkin and shaved black truffle. I’d follow that with the grilled Cornish turbot with sauce nantais, which is basically a more creamy take on beurre blanc laced with smoked caviar. With it, I’d take a side of buttered french beans with meyer lemon, some of those buttery mashed spuds in a small black earthenware pot, and maybe the glazed garden carrots, too, because they come on a carrot puree.

For pudding, I’d have the baked alaska for two, which the staff will set ablaze for me because it always brings out the child in me. If I’m going to watch the world burn, I may as well begin by doing the same to my pudding. Claridge’s never truly changes, but there’s enough happening now to keep me curious. I’m set for another 25 years.

• Claridge’s Restaurant Brook Street, London W1, 020-7629 8860. Open lunch, all week noon-2.30pm (3.30pm Sun); dinner, Mon-Sat, 6-9.30pm (last orders). From about £80 a head a la carte, plus drinks and service

• The 10th episode in the new series of Grace Dent’s Comfort Eating podcast is released on Tuesday 28 November. Listen to it here. Her new book of the same name is published by Guardian Faber at £20; to order a copy for £17, visit guardianbookshop.com