Escorts in Mount Street, W1K, as the Society arranges them after dark

Begin where the street leaves Park Lane and the mood is still residential: mansion flats, a doctor's brass plate, a gallery showing something large in a bare window. Past South Audley Street the shopfronts tighten and the street becomes itself. The oyster bar at number 20 keeps its counter busy from noon until late, and the pavement outside it is the only part of Mount Street that can reasonably be called crowded.

Walk on and Carlos Place curves away to the left, ending at a hotel door and the small fountain that flickers in front of it. Behind the north side lies a garden most visitors never find: a long strip of plane trees and benches, many of them carrying inscriptions from people abroad who loved the place, with the Jesuit church of the Immaculate Conception at its far end. At dusk in October it is the quietest square yard of soil in W1.

Guests who ask the Society for Mount Street are almost always regulars, either of the street or of the habit. They know what they want to eat, they have a view on where to sit, and they would like somebody across the table who is easy company for two hours and will not need to be told what the evening is for.

Five houses stand close enough that no car is needed at any point in the evening. No hotel on this street works with the Society in any way. They are listed because a street is easier to picture with its doors named, and because your companion has to knock at one of them.

W1K 2AL sits at the eastern end and is effectively on the street. W1K 2HP is three or four minutes north on Grosvenor Square. W1J 5EB lies five minutes south east on Charles Street, small and easy at the door. Westwards, W1K 1QA and W1K 7TN both face Hyde Park, six or seven minutes away on foot.

A private flat is visited on the same footing as any of these. The mews behind the street, and the mansion blocks along it, account for a good share of what Cressida arranges here.

The stations are further off than the street's reputation suggests. Bond Street lies about seven minutes north, where the Elizabeth line meets the Jubilee and the Central. Green Park, for the Jubilee, the Piccadilly and the Victoria, is seven minutes south east. Hyde Park Corner, which has the Piccadilly line and nothing else, takes about nine.

None of that concerns your companion, who arrives by car at whatever door you give. What it does mean is that a Mount Street evening can be walked from beginning to end: drinks at your hotel, dinner on the street, a turn through the garden if it is dry, and back again without once looking for a taxi.

Because the tables here are wanted, Cressida prefers to hear from you by teatime. She will hold a companion and book the room in one exchange, put the reservation name and the room number in writing, and leave you with nothing further to arrange. Her fee passes to her at your door, in person.

A guest with a flat off Park Street writes at four. He would like dinner at eight and company from half past seven, two hours, £1,100. Cressida proposes Bianka, who has opinions about shellfish and will not keep them to herself.

They walk the length of the street in eleven minutes because she stops at the florist's window. Dinner is a dozen oysters, a plate of something grilled and a bottle chosen after a short negotiation with the sommelier that she wins. Afterwards they take the garden gate off South Audley Street, find the benches empty, and stay there talking until the church clock makes the decision for them.

Luna, Angelika and Samanta are Mayfair residents and can be at the street's east end within minutes. Bianka and Margo come over from Knightsbridge, a quarter of an hour by car through Hyde Park Corner and less after ten.

Liana reads in this garden by day and comes down from Marylebone; Rosa follows the same route when a gallery on the street has something on. Patricia crosses from Belgravia for a table she likes. Any of the twenty-eight will come to W1K.

At the eastern end, past the fountain and its hotel, you are two minutes from Berkeley Square and its late kitchens. North across Grosvenor Street lies Grosvenor Square, where the receptions happen. West, the street ends in the traffic of Park Lane. The whole district is set out on the Mayfair page, and the shorter note on choosing where to sit may save an argument at the door.