Escorts in Grosvenor Square, W1K, with the lawns dimming as the last meeting ends

The square was laid out by the Grosvenor family in the 1720s, the first great set piece of their Mayfair estate, and for two centuries it ranked among the most fashionable addresses in London. John Adams lived on its north east corner while serving as the first American envoy to Britain, General Eisenhower kept his wartime headquarters on the square, and the whole place earned the nickname Little America.

The gardens keep that memory. A bronze of President Roosevelt stands among the lawns, a small memorial garden remembers the victims of 11 September 2001, and on the west side Eero Saarinen's long embassy building, vacated by the diplomats in 2018, still dominates the view. The rest of the square is handsome brick and Portland stone, and after dark, when the traffic on Brook Street thins, it becomes one of the calmest spots in W1.

Around it, the streets are practical and polished: Brook Street running east towards the Art Deco landmark, North Audley Street and Duke Street heading up to Oxford Street, and Carlos Place sliding south to W1K 2AL and Mount Street.

Mayfair's side streets hold a remarkable concentration of investment firms, family offices and private banks, and many of their visitors stay within a few minutes of the square. They arrive on a Monday, spend four days in meeting rooms and at client lunches, and by Wednesday evening would give a great deal to talk about anything except the deal.

That is the typical booking here: a weekday evening, a start time that depends on when the last meeting ends, and a companion equally at ease across a client dinner table and over a quiet drink afterwards. Discretion matters more than usual, and Bella treats it accordingly.

The whole south side of the square belongs to W1K 2HP, a grand old building refreshed with bright, contemporary rooms, many of them looking straight over the gardens. From its door, Carlos Place leads two minutes south to W1K 2AL, one of the most discreet grand hotels in London, whose bar is worth the visit on its own.

Brook Street leaves the north east corner for W1K 4HR, about five minutes away, with its famous Art Deco lobby. On Balderton Street, a few minutes north and overlooking Brown Hart Gardens, W1K 6TF is quietly glamorous and keeps one suite built around a giant sculpture by Antony Gormley. To the west, Upper Grosvenor Street runs down to Park Lane and W1K 7TN, where the conference and awards season keeps the ballroom and lounges busy well into the night.

None of the five has any link with us; they appear because this is where the square's visitors sleep. Your companion walks in like anyone arriving for dinner, and leaves the same way.

Business evenings rarely start on time, so Bella never expects them to. Write in the afternoon with a rough window, say between eight and nine, then confirm the exact time once you are free; she keeps your companion informed throughout. If you would rather book on the spot, plan on your companion reaching the square roughly an hour after confirmation, sometimes longer when the traffic stacks up round Marble Arch, and Bella posts the exact time on WhatsApp or Telegram once she is on the road.

For anyone arriving by Tube, the square is about 4 minutes on foot from Bond Street, 6 or so from Marble Arch and roughly 10 from Green Park, the last a gentle walk down through Mayfair; between them, those three stations cover the Elizabeth, Central, Jubilee, Piccadilly and Victoria lines. Your companion travels by car regardless, and in Zone 1 the journey is always included.

Verification works as it does anywhere: a guest name, a hotel and a room number, or a building and flat for an apartment, checked by Bella one time only in the chat. You settle her fee face to face at the start of the evening, which means no company account and no hotel folio ever shows a trace of it.

By nine on a Wednesday, Roosevelt has the square almost to himself. Across the lawn, in the lobby at W1K 2HP, a managing director visiting from abroad is on night three of five, his last call finished at a quarter past eight and his request to Bella sent from the lift, asking for a relaxed dinner and someone who could make him laugh. Walking in at nine is Rosa, curly haired, warm and gifted at loosening a formal evening.

They skip the grand dining rooms entirely. Instead she walks him across the square, past Roosevelt on his plinth, and up North Audley Street to a proper fish and chip restaurant with white tablecloths and excellent mushy peas. Over dinner they talk about soul records, baking disasters and the small gallery she found last weekend, and not one word about quarterly figures.

Back at the hotel there is a nightcap in the bar and a last hour of conversation in his suite before she leaves just before midnight. Three hours, £1,050, and a Thursday morning meeting approached in a much better mood.

The three Mayfair residents come first: Angelika, who can talk contemporary art with the most serious collector at the table; Luna, who picks the wine and is usually right; and Samanta, poised enough for any client dinner in W1. North across Oxford Street, Liana and Rosa live in Marylebone, just over the border.

From Soho, a short drive east, come Jasmin, petite and quick witted, Molly, who likes her evenings with a bit of volume, and Tiffany, rarely without a camera and always dressed with a hint of sparkle. Any of them can join you for dinner and stay on for the nightcap.

Grosvenor Square sits at a crossroads of this magazine's pages. Mount Street is two minutes south down Carlos Place, Park Lane a short walk west, and the shops of Bond Street five minutes east along Brook Street. The Mayfair page covers the rest of W1K and W1J, and Marble Arch, Marylebone and Oxford Street are looked after too, at the same rates.