Two courts of Mayfair: Annabel's, 5 Hertford Street, and the night each one keeps

One family, two front doors

Every Mayfair rivalry worth the name turns out to be a family story, and this one begins with a father and a son. Mark Birley made the basement under 44 Berkeley Square the most famous cellar in London and kept it that way for more than four decades. In 2007, the year of his death, his clubs were sold to the restaurateur Richard Caring. His son Robin went on to build a house of his own.

It opened in 2012, on the far side of Curzon Street, in a cluster of Georgian houses at the edge of Shepherd Market. 5 Hertford Street has no sign worth mentioning and a nightclub, Loulou's, in its cellars. Six years later Annabel's left the old basement for the whole of number 46, a few doors along the square, and the two houses have been compared ever since, usually by people who belong to one of them and wonder privately about the other.

Number 46: colour, a garden and a full house

The new Annabel's is a performance, and it knows it. The designer Martin Brudnizki filled a grand Georgian house with pattern, gilt, silk and flowers, and the club now runs to several bars and dining rooms over its floors, a garden terrace whose roof closes against the weather, and, downstairs, the dance floor that carries the old name forward. Even the ladies' room, a confection in pink, has admirers of its own.

It is a large club by Mayfair standards and a busy one. Members arrive from fashion, finance and every continent, the rooms are loud by eleven, and the house rewards a guest who comes ready to be looked at. A birthday, a celebration, a first visit to London that ought to feel like one: these are the nights Berkeley Square does better than anywhere else in town.

Hertford Street: small rooms and low light

Robin Birley's house answers its rival in almost every particular. The rooms are small and many, strung through the old houses on different levels, with open fires, dark paint, country-house fabrics and lamps set low enough to make everyone look rested. The effect is less a nightclub than a very private house party held in town, and conversation is the principal entertainment.

Its reputation is for privacy above everything. Photographs are firmly discouraged, the membership is generally thought to lean towards old families, politics and quiet money, and the house prefers its name kept out of the newspapers. Downstairs, Loulou's is smaller and darker than the basement at number 46 and tends to fill later. Outside, Shepherd Market takes its name from Edward Shepherd, who built its lanes in the eighteenth century over the fairground of the old May Fair, so the whole of Mayfair owes its name to the few streets beyond the door.

What to wear to each

Neither house publishes every rule, and codes shift, so the member who invites you is the authority on the night. The broad lines have held for years, though. Neither is a place for trainers, sportswear or a cap, and a gentleman in a well cut jacket is never wrong at either door.

Choosing by the night you want

For a visitor the rivalry matters less than the question it hides, which is simply what kind of night you would like. Cressida puts it to guests in terms of volume.

Your companion, on a member's invitation

Both are members' houses, and a companion enters exactly as any guest does: named by the member at the door, signed in, and bound by the club's rules from that moment. The Society holds no memberships and asks nobody for favours, so the invitation must be yours or that of a friend in your party. The general customs of the desk are set out in the note on Mayfair's members' clubs; what follows here is particular to these two.

Tell Cressida which house, the hour of your table and whether the evening is likely to end downstairs. Your companion dresses for that address rather than for a general idea of Mayfair, arrives with you or meets you on the pavement outside, and keeps her telephone in her bag until she has left the street. Neither basement is at its best before midnight, so these evenings are usually booked long, and nights out in clubland describes how the Society shapes them.

Company for either court

Lea looks at interiors the way a sommelier looks at a list, and number 46, where every wall has an argument to make, delights her; she will have an opinion about the ceiling before the first glass arrives, and she is one of three auburn and red companions on the roster. Margo prefers old gold, bias-cut silk and rooms that have been lived in, and she is the natural guest for Hertford Street, calm in low light and in no hurry to explain herself. She sits among the companions in their thirties.

For a first visit to either house Cressida usually suggests the dinner date; its four hours, at £1,800, begin at a table nearby and end wherever the member's evening ends. Mention the club when you write through booking. The restaurants around Annabel's have a note of their own, arranged by direction, and every hotel on Park Lane sits within a few minutes' walk of Hertford Street.