Knightsbridge, SW1X and SW7: the district where she is already home

SW1X is the eastern half: Brompton Road with Harrods on it, the Sloane Street corner where Harvey Nichols stands, and the white squares behind that fall silent the moment you leave the main road. SW7 is the western half, running towards the museums, greener and slower, holding the Bulgari and the mews streets behind it.

The two halves behave differently after eight. The eastern side empties as the shops close and refills around the hotel bars. The western side barely alters, which is why guests wanting a genuinely quiet evening ask for that end of the postcode.

Six hotels sit inside five minutes of the station, and a companion who lives here recognises every lobby on sight. They appear below because that is where guests sleep. None has any tie to us, sought or otherwise.

Facing the park across Knightsbridge itself is Mandarin Oriental Hyde Park, SW1X 7LA. Three minutes west, on the SW7 side, The Bulgari Hotel, SW7 1DW. Jumeirah Carlton Tower, SW1X 9PY, stands over Cadogan Place. The Berkeley, SW1X 7RL, holds the Wilton Place corner nearest Hyde Park Corner, with The Wellesley, SW1X 7LY, small and immediately beside it. The Knightsbridge Hotel, SW3 1PT, is five minutes south in the quiet streets.

Knightsbridge station sits 1 minute off Brompton Road on the Piccadilly line, which runs straight through to Green Park and Piccadilly Circus and out west to Heathrow. Hyde Park Corner is 5 minutes east along the same line. Sloane Square, 9 minutes south, brings the Circle and District lines.

Where a companion is coming from elsewhere she takes a car, and the first two zones are already covered by the fee. From this postcode, frequently, nobody travels anywhere at all.

Elsewhere in London an hour of notice is a promise with a car inside it. In SW1X it is a walk. Where the companion you want is one of the three who live here, and she is free, twenty minutes is realistic, and Octavia will say so rather than pad the figure.

The confirmation does not change. A hotel wants your full name and a room number; a house wants the floor, the door and whatever the bell says. It is written once. She takes her fee at the door, and there it ends.

Guests in the park facing suites, who have spent the day in meetings across town and have no intention of crossing it again. Residents of the squares behind Brompton Road. Visitors who came for the shops and worked out that the evening beats the afternoon. What they want is someone unhurried, well dressed, and comfortable in a very quiet room.

Half past six. A guest at The Berkeley writes for three hours from seven, an early table so the evening is not all restaurant, and a companion who knows the district. Octavia proposes Sonya, who lives eight minutes away and carries herself like the lifelong ballet class she still attends.

Seven o'clock. She is there at five to. They eat early, as asked, then walk up into the park as far as the Serpentine and back down Wilton Place. She names three scents from across the table, correctly, which he disbelieves until the third. Three hours, £1,500, and she walks home.

Bianka keeps notebooks of everything she has tasted and can recall a glass years later. Margo reads auction catalogues for pleasure and plays piano after dark. Sonya is the stillest of the three, and the most precise.

Ten minutes east, in Belgravia, are Lea, Patricia and Violetta. Michelle travels up from Chelsea and Lucy from Pimlico, each about fifteen minutes at that time of evening.

Hyde Park Corner is the hinge. Five minutes east of it lies Park Lane and its hotel row, and past that the whole of Mayfair. Green Park is two stops on the Piccadilly line, with Piccadilly and St James's a short walk on from there. Terms are identical across every one.