John Caudwell House at Audley Square, a Mayfair Megamansion Rebuilt

The John Caudwell house is the building most often named when the press reaches for the most expensive house in the UK. It stands at Audley Square in Mayfair, it took the better part of a decade to build, and almost all of what makes it remarkable is below ground. Very little of the John Caudwell house is visible from the street.

It is worth setting beside a building like Gainsborough Old Hall, because the two answer the same question (what does a very rich household build for itself?) five and a half centuries apart, and the answers are almost exactly inverted.

The John Caudwell house and Audley Square before it

Audley Square is part of the Grosvenor estate's eighteenth-century development of Mayfair, laid out when the fields north of Piccadilly were turned into the most systematically planned rich district in Europe. The site had been institutional for most of the twentieth century, latterly offices, and it came to market as a development opportunity rather than as a house.

John Caudwell, who built and sold the mobile phone retailer Phones 4u, acquired the Audley Square property in the early 2010s. What followed was not a refurbishment. The existing structure was substantially rebuilt and the ground beneath it excavated to a depth that required years of piling and removal, on a constrained site in one of the most tightly controlled conservation areas in London.

What makes it the most expensive house in the UK

Three things, in combination. Location: Mayfair land is priced as the scarcest asset in British real estate. Scale: the finished floor area runs to tens of thousands of square feet, which for a single household in central London is extraordinary. And specification: the reported programme included pool, spa, cinema, art gallery and staff accommodation, most of it in the excavated levels.

The title of most expensive house in the UK is a press construction and not a measured fact. Private sales are not published, and valuations attached to a property nobody is selling are estimates. What can be said is that no other single-family house in the country has attracted comparable reported figures, and that the John Caudwell house is the reference point everyone else is measured against.

Mayfair and the return of the single-family palace

For most of the twentieth century the direction of travel in Mayfair was the other way. The great aristocratic houses were demolished or turned into embassies, clubs and offices, because no private household could staff or heat them. What has happened since the 1990s is a reversal: individual owners have been buying back and reconsolidating buildings that had been divided into flats and offices, and turning them into single residences again.

Mayfair is where this is most visible, because that is where the stock and the buyers are. The constraint is that almost every building is listed and the whole area is a conservation area, so the only direction available is down. Basement excavation is the defining London practice of the period, and it is why a house of this kind reads as modest from the pavement.

The megamansion as a building type

A megamansion is not simply a large house. It is a building type with recognisable features: a restrained street elevation, an enormous subterranean programme, and an internal plan organised around leisure and security instead of the reception of guests. The medieval hall did the opposite: the biggest, most impressive room was the one strangers were brought into first.

That inversion is the interesting thing about the megamansion, and it is the reason a site about a fifteenth-century manor has any business discussing one. Both are the maximum a household could build in its moment. The Burghs put their money into a room designed to be seen by everyone who came to the door; the modern equivalent puts it into rooms designed so that nobody knows they are there. Other examples of the type are covered on the royal mansions page.

Questions about the house