The new restaurant on the ground floor of Fortnum & Mason does breakfast, lunch and dinner exceptionally well

Standing proud at the corner of Jermyn Street and Duke Street in the heart of St James’s, this newly opened dining room and bar manages to combine all the traditional charm of its postcode with a sleek interior and a contemporary, yet comforting, all-day menu.

Located on the ground floor of Fortnum & Mason—in place of the erstwhile slightly fusty Fountain Restaurant—45 Jermyn Street’s rust-red orange awnings and sumptuous curved leather banquettes contrast brilliantly with the store’s distinctive duck-egg blue paintwork. Best of all, however, is that, as it’s open from 7am until midnight every day, it’s possible to dine like Alice in Wonderland at breakfast, lunch and dinner. Early morning delights include everything from the good old full English and Marmite-slathered crumpets to crushed avocado on toast with a Bloody Mary sauce.

Lunch offers the chance to indulge in the caviar trolley, which sees diners choose from Iranian Beluga 000, Golden Oscietra and Siberian Sturgeon, served with scrambled eggs (cooked at the table on the trolley’s hot plate), miniature baked potatoes and warm blinis—bliss.

For supper, I feasted on dressed Portland crab, followed by perfectly cooked red-legged partridge from Swinton Estate in North Yorkshire, with crispy fried polenta and Jerusalem artichokes, rounded off by an impressively tall meringue-topped knickerbocker glory. If you’re after a real treat, it doesn’t get much better than this (020–7205 4545; http://45jermynst.com).