The capital’s super rich residents have been extending their homes beneath ground, making space for swimming pools, wine cellars and gyms.

In the last decade alone, 4,650 basement conversions have been approved.

All together, the basements have a total of about 550 cinema rooms, 340 games rooms, 240 saunas or steam rooms and 60 underground garages.

Two of the basement conversions even had more than one swimming pool in them.

The research found that 785 of them were considered to be “large”, spreading across at least two storeys, or one level that extends beyond the house and under the garden.

Another 112 of them were “mega basements” which meant they were at least three storeys deep or two levels that stretched under the garden.

The report - Mapping Subterranean London: the Hidden Geography of Residential Basement Developments - also aims to highlight the “environmental concerns” about extending so far underground.

Researchers looked at seven boroughs: Camden, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Westminster and Wandsworth.

Many of the super basements were located in Kensington and Chelsea along with Hammersmith and Fulham.

A report into the study read: “Although some of these standard basement developments may be quite modest, a significant number of them contain amenities that suggest a high degree of ‘luxification’.”

The report added: “Some can take many years of disruptive construction to complete and concerns have been raised about their environmental impact.”