The third person in the car: chauffeurs, briefings and the door held open

In most evenings, one person sees more than anyone else, and it is the driver. He sees who is collected and where, hears the conversation in the back and knows exactly when the evening ended. A good chauffeur has forgotten all of it by morning. That is his profession, and the best in London practise it as a point of pride.

Still, a car is a room with a third person in it, and it helps to treat it as one. The courtesies involved are small and old, and a companion who knows them will notice, quietly, whether you do.

A driver needs times, addresses and names. He does not need a reason. The briefing for an evening with a companion is the briefing for any evening with a guest: collect at seven from the hotel on Albemarle Street, dinner at eight on Jermyn Street, wait nearby, home at eleven. Her first name, if he is to collect her, and nothing more.

Hotel concierges and chauffeur firms are used to guests who say little, and saying little is itself a signal they understand. Telling the driver more, an explanation, a knowing joke about the evening, places him in an awkward position and your companion in a worse one.

In a chauffeured car in Britain, the seat of honour is at the back on the left, behind the front passenger. It opens onto the kerb, so your guest steps straight onto the pavement rather than into the traffic. Offer it to her. You take the seat behind the driver and walk round the back of the car to reach it.

The front seat beside the driver belongs to a colleague or a security man, never to a guest. If she is collected alone, she sits at the back on the left, as any client of the car would. A black cab is different: the back is a bench with fold-down seats facing it, so she takes the bench and you take whatever place leaves her the most room.

A London black cab has a glass partition between the driver and his passengers, with an intercom for instructions, and in one you may talk with a little freedom. Most chauffeured saloons have no partition at all; a few long cars have one, often more for show than for silence. Assume the driver hears everything, because he usually does. The same holds for the telephone: a call about the evening made from the back seat is a call made to three people.

Talk in the back as you would across a restaurant table: warmly, and without anything you would mind a stranger overhearing. Arrangements, timings and anything to do with the terms of the evening belong in writing with Octavia, not in the car. Her fee is handed to her in private when she arrives, never across the back seat under the eye of the mirror.

Few gestures are older, or more noticed, than the car door.

Some guests prefer to send their own driver to collect a companion. It works well, on two conditions. Octavia passes her the colour, make and registration of the car and the driver's first name, and the driver is given her first name and the place she will be waiting, which is never her home. She then arrives in your car, already settled, and the evening begins at the kerb rather than in the lobby.

Most guests find it simpler to let her arrive on her own, which she does anywhere in Zones 1 and 2 as part of the fee. The driver is then yours for the rest of the night, and the first moment of the evening belongs to a hotel bar, which is pleasant too.

During dinner a good driver waits nearby rather than at the door, and comes when summoned. Give him a rough time and send him a message if the evening runs on; he would rather know than guess. At the end of the night, the car is the last room of the evening. Keep it as courteous as the first.

If the evening ends with her going home separately, the goodbye happens on the pavement, not through a closing window. Wait until her car has pulled away before you get into your own.

Molly, who has a soft spot for old roadsters, will know the car before the driver has introduced it, and she likes an evening that starts late and runs long. Tiffany loves hotel lobbies and the moment of arrival, and carries a silent-shutter camera she never raises without asking. Both are among our brunettes. Sonya, calm and upright from a lifetime of ballet class, makes an evening by car feel like a short journey between two good rooms.

For a dinner that needs a car at each end, the four hours of the luxury dinner, at £1,800, leave room for both drives. Shorter and longer bookings appear on the rates page. One line to Octavia through booking starts the arrangement.