Night out companion in London, and why the route is planned together

Begin in St James's Place around nine, where the martinis are mixed at a trolley beside your chair and are famously strong; one is plenty. Walk on to Bentley's on Swallow Street for oysters at the counter, or to Quaglino's on Bury Street, where there is a band and a staircase built for an entrance. For something quieter, the American Bar at SW1A 1NJ keeps its ceiling of ties and caps and a low murmur until late. After midnight the choice lies between a cigar terrace in St James's and a jazz room in Soho, where the late set starts whenever the musicians feel ready.

The notebook has the martini hour in St James's Place and the cigar terraces of St James's, both worth a look before you go out.

The best nights out are planned in outline and improvised in detail. Tell Octavia the mood you are after: jazz or a band, loud or low, a club or no club at all, and whether dinner belongs in the middle of it. Your companion arrives with a route already in her head and abandons it cheerfully if the two of you find somewhere better on the way.

A show makes a good opening. The theatres of the Haymarket and Shaftesbury Avenue are a short walk from Piccadilly Circus, and a curtain at half past seven leaves the late part of the night entirely intact.

Molly likes her nights late and long, opening in a gilded bar and closing wherever the music improves. Stacy, very tall and deadpan, comes into her own after eleven and keeps a list of comedians worth the ticket. Jasmin dances salsa on Tuesdays and can recite the history of every stirred classic on the menu. Tina files her records by mood and keeps a bartenders' notebook. Angelika would end the evening beside a trio close enough to hear the brushes, in a set that runs long.

Jasmin and Tina are two of the petite companions, which in a crowded bar means only that they reach the counter well before you do.

The clubs of Pall Mall close their doors to non-members early, and the hotel bars along Piccadilly thin out after one. Soho is a short walk east across Regent Street and stays awake far longer; Mayfair keeps a handful of late rooms of its own. Your companion crosses whichever line the night requires. Her journey adds nothing inside Zones 1 and 2, while the drinks, the tables and any cover charge fall to you as host.

In summer the night starts outside: a glass on a terrace while the light lingers over Green Park, then a pint standing on the pavement of a Victorian pub off Jermyn Street, as the neighbourhood's bankers and tailors do. In December the arcades are lit for the season and the hotel bars are at their most festive, and the good tables go early, so a few days' notice is wise.

In a busy bar nobody needs to know how the evening was arranged. To the barman and the doorman she is simply the person you came out with. She drinks at your pace or a little slower, keeps an eye on the time for both of you, and makes sure the last stop is one you remember with pleasure rather than with a headache the next morning.

However late it runs, the evening finishes where you are staying. Your companion rides back with you or sees you into a car, and says goodnight at the hour agreed. If the night is going well and you would like another hour, ask her or send Octavia a line; if her diary allows, it is confirmed in writing before it begins. Booking explains how the first message sets all of this up.