The duo: two companions, one evening, and a reason they belong together

Cindy and Michelle both live in Chelsea and both crew on boats; seat them at one table and the talk turns to tides and harbours before the menus arrive. Rosa and Tina keep soul records on vinyl and will cheerfully disagree about pressings; both are among the petite companions, and both laugh easily. Nora and Tiffany share a weakness for grower champagne from small houses, which turns the wine list at dinner into a joint project.

These are starting points, not a menu. If you have met two companions separately and liked them both, say so, and Octavia will ask each whether the idea appeals.

A birthday. The close of a long negotiation. The last night of a visit that went well. A table at Sketch where a third chair changes the whole atmosphere, or a private dining room at a club on Dover Street where you are the host and would like the room to feel full. The duo is at its best where there is something to celebrate and space to celebrate it properly.

It also suits evenings that are sold in threes: a box at the opera, three seats at a charity auction, a table at a supper club where an empty chair would be noticed.

Ask the restaurant for a round table, or a corner banquette; a long table is unkind to three people. The two companions will draw you into the conversation rather than talk across you, and between them they tend to cover more ground than any pair of dinner guests you have hosted: sailing and records, champagne and design, whichever the pairing brings. Unless one of them has been booked for longer, they leave together too.

An evening at your hotel works on the same principle. Think of it as a small drinks party in the sitting room of a suite, with a bottle chosen by Nora or Tiffany and a conversation that never runs dry.

Each companion keeps her own place on the ladder. Two hours is £1,100 for each of them; the four-hour dinner is £1,800 for each. Octavia writes both figures in the thread, side by side, before you agree, and each companion receives her own fee from you, in person, when she arrives. Nothing is added for the pairing itself. The ladder in full is on the rates page.

The two are easily confused. A duo is one guest with two companions; a couples evening is two guests with one. If you are bringing a partner, the second is the right arrangement, and Octavia will gently say so.

Two diaries take longer to align than one, so a day's notice widens the choice considerably. Same-day duos do happen, though the pairing then depends on who is free. For a hotel evening, a suite with a sitting room suits three people far better than a double: The Ritz, or the larger rooms at Brown's on Albemarle Street, are both well suited.

The notebook covers dining in clubland as a guest, and the unhurried evening on pacing, which asks a little more choreography when there are three of you.

A duo is company doubled and nothing else. The conditions are those of every arrangement: time and companionship, nothing further, and a request beyond that ends the evening for both. Booking explains the check made before they set out, which is made once for the pair.