IT HAS 17 bedrooms and garaging for 10 cars, outdoor and indoor swimming pools, loudspeakers embedded in the grounds for garden parties - and an en suite panic room.

A buy-to-let millionaire raised in the East End is redeveloping a house in north London that could sell for £85m, which would make it the most expensive property in Britain.

Andreas Panayiotou, 41, the son of Greek Cypriot immigrants, last year paid £14m for East Weald, a 23,000 sq ft, grade II listed Edwardian house. It is located on The Bishops Avenue in Hampstead, known as “billionaire’s row” and home to members of the Saudi and Brunei royal families.

Panayiotou, whose fortune is calculated at £715m in The Sunday Times Rich List, plans to renovate East Weald, at No 59, and double its size to 40,000 sq ft. It will have two acres of landscaped grounds.

“It’s going to be the best you’re ever going to see - there’s nothing we’re not putting in there,” the entrepreneur said, speaking from his 200ft yacht, moored this weekend off the Italian resort of Sorrento, where he is on holiday with his wife Susan and his five children.

“The only thing it doesn’t have is a helicopter pad.”

He is using 12 types of Italian marble and seven types of wood for the bathrooms. The snooker room, office, bar, library and grand staircase will be clad in oak, while all the carpentry work is being done in Italy and flown over, along with the hand-carved marble basins and baths.

With security paramount for any future owner, the panic room, off the main bedroom, will have its own lavatory, basin, control panel and separate telephone wires that cannot be cut.

Outside, Panayiotou is recreating an Edwardian-style garden. He is also restoring the original lead guttering and drainpipes that are engraved with wild animals such as deer, rabbits and hares.

“Bringing something like this back to its original glory is unique in itself,” he said.

Panayiotou, whose parents moved to Britain in 1959, was raised in Bow, east London. He became an amateur boxer aged seven and wanted to turn professional, but his parents persuaded him to join the family dry cleaning business instead.

Panayiotou inherited the family firm in 1996 but made his fortune by converting run-down offices, warehouses and hospitals in East London into flats. His business, Ability Developments had net assets of £190m by 2004-5, with about 2,500 flats in London.

Earlier this year Panayiotou sold £205m worth of his residential portfolio. He is moving into the hotel business.

“Residential property has [risen] too far,” he said. “That’s why I’ve diversified.”

He was originally offered East Weald as a development opportunity, but considered moving in when he saw how close it was to his office in Portland Place. He and his family would have lived in the main house and built two properties on the surrounding land, which could have sold for £12m.

However, when his wife compared the two acres in London with the 20 at the family home near Epping in Essex, they decided to develop East Weald as a single property, cashing in on the booming London market. “At the upper end there’s still big demand,” said Panayiotou. “You’re not expecting the City boys to afford a property like this - it’s going to be a Russian, an Arab or maybe an Indian.”

Panayiotou was reluctant to predict how much East Weald would fetch, but Trevor Abrahmsohn, a director of Glentree Estates, said it could sell for more than £80m. “In this area, you could justify anything up to £2,000-£2,500 per square foot. It could easily go on at £85m.”

Panayiotou may, however, reconsider the sale. “I wouldn’t rule out my wife changing her mind and moving in,” he said.

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