Harrods after the tour groups, an early supper in the store and Knightsbridge after dark

Harrods began in 1849 as a small grocery in what was then a village on the edge of London, and the vast terracotta building on Brompton Road was completed in the Edwardian years. Today it is one of the most famous shops in the world, which is precisely why timing matters for a date. At midday the ground floor is a river of visitors. Late in the afternoon, when the tour groups have moved on and the office crowd has not yet arrived, the store becomes a different, far more pleasant place.

The restaurants follow the store's trading hours, so dinner at Harrods is an early dinner by definition, and on Sundays, as with every large shop in England, the day is shorter still. Check the day's hours on the store's own website before you plan, then treat Harrods as the overture, with the main act elsewhere. That main act belongs to Knightsbridge itself, and it is wonderful.

The Food Halls are what everyone photographs, with their ornate tiled walls and ceilings. What fewer visitors realise is how seriously the store now takes sitting down to eat. The Dining Hall, set in one of the restored tiled halls, gathers several kitchens under one extraordinary ceiling, and you choose from counters rather than from a single menu. It is lively rather than hushed, and it suits a first meeting well: there is always something to point at, the talk never stalls, and nobody feels watched.

Elsewhere in the building, dining counters and cafés cover everything from oysters to pasta, and the offer changes often enough that the best advice is simply to walk through and see what appeals. The one constant is quality. Harrods does not do ordinary food. Before or after you sit down, a slow circuit of the halls together is a pleasure in itself: the chocolate counters, the cheese counter, and the wine shop below street level, where the rarer bottles are kept like museum pieces.

For a quieter first hour, head upwards. The Tea Rooms, on an upper floor, serve afternoon tea in a light, elegant room that feels a world away from the crowds below. Ladurée, the Parisian macaron house, has its own tea room by the Hans Road side of the store, all pastel colours and gilded mirrors, and it is an easy place to meet.

Getting between floors is part of the fun. The Egyptian Escalator, lined with sphinx-like figures and hieroglyphic decoration, is one of the most theatrical staircases in London. It leads, eventually, to the Salon de Parfums, six floors up, a hushed temple of rare fragrance where Jasmin, petite, quick to laugh and able to name the perfume across any table, will have you smelling a dozen blotters before she chooses one for your wrist, each scent introduced with a small and rather wicked character sketch.

A simple structure makes a Harrods evening feel planned rather than improvised:

Step outside as the store closes and the light has changed. The terracotta facade is lit by thousands of bulbs, Brompton Road quietens, and within two minutes you can be somewhere entirely different. Beauchamp Place, a narrow street of small restaurants and boutiques, opens almost opposite. Hans Place, behind the store, is a quiet garden square where Jane Austen once stayed with her brother. And a short walk south, the hotels around Cadogan Place and Sloane Street offer a proper bar for a second drink.

Milena, dark haired, 175 cm and gloriously direct, is fond of the Carlton Tower's Chinoiserie lounge, a few steps from Sloane Street, for the first or last drink of an evening; she picks the seat that commands the doorway and has quietly judged every table before the glasses land. She is one of the raven haired portraits, and Jasmin belongs to the early twenties set.

Harrods rewards longer bookings. Three hours, £1,050, cover the three acts comfortably. Four hours, £1,300, booked as dinner at the corner table, allow an early supper in the store and a second table elsewhere, or a slow walk back to your hotel. Daytime and evening are priced alike, and Knightsbridge lies inside the zone where travel is already included.

What you pay her covers her time and her company, nothing else, and it changes hands privately, never at a counter or a till. Everything else, from the Dining Hall to the taxi, stays with you as host. Once the plan feels right, pass it to Rosie through the booking page, with the door number if you already know it.