Flat the size of a broom cupboard – yours for £89,000

But it's perfect for a billionaire's servant (or anyone who needs central London parking)

The grand entrance in Knightsbridge and the flat itself as viewed by Nick Clark (Susannah Ireland)

With the battle for property space in central London becoming ever fiercer, many joke that they live in a broom cupboard. Now, a London flat that was actually converted from a broom cupboard, has been put on the market for £89,000 despite the fact it is not much bigger than a snooker table.

The flat is on the eighth floor of a block overlooking Harrods in Kensington and Chelsea, the most expensive borough in the country.

Matthew Fine, managing director of Hunters estate agents, which is looking after the sale said: "It's the smallest flat I've ever seen in my life. In 30 years of being in the business, I've never seen anything this small".

Sufferers of claustrophobia certainly need not apply: it is hardly a stretch to touch both sides of the one-room flat which has a built in toilet area that doubles as a shower room. There is space for a small bed, opposite the kitchenette.

The firm says it has already had a high level of interest. The property was advertised online shortly before last weekend, and attracted a remarkable 100 responses, and there have already been over 30 viewings leading to five firm offers. "I can't believe the response, it's phenomenal... These were originally storage cupboards for the porters, with brooms in them and stuff like that. In the 1970s they converted them into flats and sold off as studio apartments."

The marketing blurb describes the space as an "ideal pied-à-terre or rental investment for aspiring buyers looking for something a bit different". Mr Fine said that valuing such a novelty property had been tough, but current bidding has taken its value over £120,000. All five to put in firm offers were cash buyers. He believes that some may be keen to secure the flat to put up domestic staff. Another benefit is the resident's parking permit that comes with it. A garage in the area can cost up to £250,000 – most are bigger than the flat itself.

There are nine such flats in the Prince's Court building on the Brompton Road, and they are all slightly different sizes.

The estate agent admitted that the tiny flat would not pass the council's health and safety laws, saying it would be classed a fire hazard.

One in the same block that was even smaller sold for £120,000 in 2006 and was put back on the market at £200,000 two years ago.

Around the corner in Chelsea a former janitor's storeroom, measuring 11ft by 7ft, went on sale in 2007 for £170,000. The smallest house in Britain is in Wales. Quay House is 10ft by 6ft and was lived in until the turn of the 20th century.