The cigar terraces of St James's, and the long last chapter of a formal evening

A good cigar lasts an hour or more, and it cannot be hurried. That is exactly why it belongs at the end of a formal evening, after the plates have gone and before the car is called, when there is nothing left to do but talk. In St James's the habit runs deep. The clubs smoked for three centuries, the tobacconists of St James's Street supplied them, and the quarter keeps more of the old cigar culture than anywhere else in town.

The difference today is that the last chapter is taken outdoors, under a heater, with a blanket within reach.

Since 2007, smoking has been prohibited in enclosed and substantially enclosed public places in England, and that includes every bar, restaurant and hotel lounge. A covered terrace counts as outdoors only when more than half of its walls are open to the air. That is why London's cigar terraces look the way they do: a roof or awning, heaters overhead, blankets folded on the chairs, and sides that let the night in.

There is one narrow exception. Specialist tobacconists may let customers sample cigars and pipe tobacco on the premises, which is why a few of the old shops keep a room where a cigar can be chosen and tried. It is a shop's tasting room, not a lounge for the evening, and the terms of using it are the shop's own.

Hotel rooms, almost without exception, are non-smoking, and many hotels charge for the cleaning if a cigar is lit upstairs. Keep it for the terrace.

The quarter's cigar history fits into a few hundred yards. James J. Fox, at 19 St James's Street, trades from a shop that has sold tobacco since the eighteenth century and keeps a small museum of its past customers, Churchill prominent among them. Davidoff holds the corner of Jermyn Street a few doors away. Both are the places to choose a cigar properly, with advice, before an evening rather than at the end of it.

Buying in the afternoon and smoking at night is the old way, and still the best. Ask the shop to cut the cigar for you, keep it in a tube for the evening and tell you roughly how long it will last, which matters when a table is booked for nine.

Dukes London keeps a cognac and cigar garden at its house on St James's Place, which makes it the most natural close to an evening that began with a martini indoors. Several of the grand hotels across Piccadilly and around Park Lane keep terraces of their own, and some private clubs in Mayfair have smoking gardens for members and their guests. Arrangements change with the season, so ask your hotel's concierge where the nearest one is before dinner rather than after.

In winter the heaters do their work and the blankets come out, and a terrace at midnight in January can be the snuggest corner of the whole evening. In summer the same terrace is a garden, and the cigar becomes an excuse to stay outside until the sky over the rooftops has gone fully dark.

Cigar etiquette is mostly common sense, with a few details worth knowing.

Not everyone who enjoys a cigar terrace wants to smoke, and a companion is never expected to. Mention the plan when you write to Octavia, so that the companion she proposes is one who genuinely likes the ritual, or at least the company it brings: a glass of something aged, a blanket, a courtyard at night, and the sort of talk that seems possible only when an evening is nearly over.

Think of the practicalities, too. Seat her upwind. Offer the blanket before she has to ask. Keep the cigar a moderate size if she is sitting close, a robusto rather than a double corona. And if the evening continues somewhere else, remember that smoke travels on clothes; a few minutes of fresh air on the walk back is a kindness to you both.

Cognac is the classic partner, and an older one is better. Armagnac, a little more rustic, is the connoisseur's choice. Aged rum and single malt whisky both have loyal followers, and a glass of port is traditional in the clubs. Strong black coffee suits a cigar better than most people expect. Whatever you choose, sip it slowly; the glass should last as long as the cigar.

Violetta, tall, composed and very dry, is perfectly at home under a heater at midnight and in no hurry for the evening to end; she is one of our statuesque companions. Margo, who likes her rooms vintage and her silences comfortable, enjoys the ritual more than most. Michelle, warm and chatty, will know the terrace waiter by name before the cigar is lit.

A dinner followed by the terrace suits the four hour dinner at £1,800. For a later night that moves on afterwards, the late invitation is written for exactly that. Each duration and its figure is printed on our rates, and an evening in St James's starts with one message through booking.