She comes to you: suites, apartments and front doors across the West End

The half hour between your message and the knock

Delphine answers with three things: who, how much and when. She will not confirm an hour she is not certain of holding. Your companion then dresses for wherever she is going, carries nothing that announces why she is going there, and comes by cab. One further line reaches you as she turns into your street, so the door is never answered in surprise. No flowers arrive ahead of her, nothing is left downstairs in anybody's keeping, and no member of staff is told which floor she is going to.

Once the door has closed

The first few minutes are the ones guests worry about beforehand and the ones that need least managing. She takes off her coat, accepts whatever you happen to be pouring, and asks about your day rather than about the room. By the time the glass is half empty the conversation has usually found its subject, and from there the hour is simply spent in good company.

If supper is coming up to the suite, say so when you write, so that she has not eaten before setting out. If you would rather walk out for part of a two hour booking, she will have looked at the street on her way in and will know which door along it is still worth trying at that time of night.

Suites, serviced flats and private houses

Most often it is a suite. The porters in the great lobbies of Mayfair and Knightsbridge stopped looking twice at a well dressed arrival a generation ago, and she gives them no reason to start. She walks in as your guest, takes the lift as your guest, and has no business whatever at the desk.

Serviced flats behind the shops and lateral apartments off the garden squares are just as ordinary in the day book, and a fair number of appointments here are private houses where the porter has already admitted forty people that evening. Wherever it happens, the whole of it stays behind your own door and none of it remains there afterwards.

What Delphine wants before she sends anybody

Two facts, asked for once. Which hotel, and under what name and number the room stands. Or, if you are at home, the street and the floor. Nothing beyond that. The front desk is never telephoned, you are asked for no papers of any kind, and the lines you send are held only while the appointment is live and are then let go. The courtesy of it runs both ways, and it is what lets a circle this small stay certain of who is on the far side of every door.

Choosing how long

The hour at £250 does not pretend to be long: a drink, a proper introduction, a conversation that has only just found its feet. Ninety minutes at £400 is the length the daylight appointments take. Two hours at £500 is where most first evenings settle, with room for supper somewhere close by. Three hours at £700 lets a curtain or a private view sit inside the evening without anybody hurrying afterwards.

Past that the appointment becomes the long table or dinner until morning. Nothing here is run against a stopwatch, and where the day book has room in it an evening can be extended while it is still going, at the next rung up.

Who tends to be closest

Angelika, Luna and Samanta sleep inside Mayfair and are frequently a few streets from the address written to us. Lea, Patricia and Violetta keep the same habit in Belgravia and rarely leave it after dark. Bianka, Margo and Sonya do the same in Knightsbridge. The figure does not move with the name, so choose the face in the Salon and leave the geography to Delphine.

If the hour has to move

Plans slip and the day book expects it. Warning of three hours or better costs you nothing at all. Closer in than two hours, one half of the agreed sum is owed, and a door that goes unanswered is owed whole, with fifteen minutes of latitude on the start. A meeting that overruns needs one line to the switchboard, and Delphine will say straight away whether the later hour is still free.

If anything delays your companion, you are told at the time and offered another hour or another name. Her lateness is never taken out of your hours, which begin at the door rather than at the time written down.