London property madness: 10-bedroom ruin on sale for £22.5m on Hampstead's Billionaires Row

It is a 10-bedroom Victorian mini-mansion set in 1.7 acres of land on the fringes of the highly sought-after and exclusive Hampstead area of north London. It sits on The Bishops Avenue, known as 'Billionaires Row', where a number of sultans and Arabian princelings own houses. Yet there are a couple of catches.

Even the estate agent calls it "a dilapidated house" and it has a price tag of £22.5m – 42 times the city's average house price. At least it's a freehold and is now reduced in price from its attempted 2012 sale at £25m.

The property, Kenmore House, is marketed by Mann Smith, which says it had planning permission – now elapsed – to add an extension and part-rebuild the house – or, if the council agrees, you could make a fortune by developing it into luxury flats. "From initial conversations with Barnet planning department, there is potential to develop a scheme of luxury apartments incorporating part of the existing building," says the sales brochure. "However, interested parties are required to make their own enquiries. A subject to planning deal will be considered."

The Bishops Avenue near Hampstead Heath is notorious for its empty properties, which are worth hundreds of millions of pounds on London's soaraway market. More than a dozen of the properties on the street are empty, working as de facto cash vaults storing the riches of their super-wealthy owners. Billy Butlin, founder of the holiday camp empire which bears his name, and Lakshmi Mittal, a steel magnate who was once the wealthiest man in Britain and third-richest in the world, are just two of the many high-profilers and former residents on Billionaires Row. Richard Desmond, the media and pornography baron, currently has a home on the road.

But if you don't want to buy the dilapidated Kenmore House and go through the trouble of planning and development, you could, for the same price on the same road, buy a luxury eight-bedroom house with a cinema room, indoor swimming pool and whirlpool bath, staff living quarters and a detached office. It belongs to Celia Sawyer, a wealthy interior designer who appeared on Channel 4's Four Rooms as an art dealer, who has put it up for sale.