For sale: London's £50m house

It first went on sale for £30 million - but unlike the rest of the property market the price tag just kept soaring. This London home jumped to £35 million and now potential buyers are being invited to make offers of around £50 million. That makes the house the most expensive on the market in Britain today.

Toprak Mansion is on The Bishop's Avenue in Barnet. It is owned by Turkish industrialist and banker Halis Toprak.

Mr Toprak, 67, spent almost five years building the neo-classical edifice to his own exacting specifications.

Little is known about Mr Toprak, a Turk of Kurdish extraction who founded the Toprak Holdings group, a sprawling Istanbul-based conglomerate covering pharmaceuticals, building materials and textiles.

But a clue as to why Mr Toprak might be selling his trophy home can be found in the recent troubles of his business empire.

In 2001 his bank, Toprakbank, then the 20th biggest in Turkey, was seized by the Turkish government and placed in receivership. In a statement, Turkey's Banking Supervisory Board said Toprakbank was "a threat to the stability and confidence of the financial system" because of its bad loans.

To make matters worse, earlier this year Mr Toprak's magnificent £5 million 100ft yacht Princess-T was seized by the Turkish Savings Deposit Insurance Fund in the resort of Marmaris.

At 28,000 square feet, Toprak Mansion is around five times the size of the average large detached family house - and that does not include staff and guest apartments.

The sales particulars detail an 80ft "grand salon" with a terrace overlooking the garden and a dining room seating 40 people. The entrance hall has a double staircase and a glass passenger lift.

There are four kitchens, the main one having a dumb waiter to the dining room and a walk-in cold store. An indoor leisure complex features a large swimming pool, Turkish bath and sauna.

The first-floor master bedroom suite has a bathroom, salon, dressing room, meeting room, office and kitchen. There are six further bedroom suites.

The two-acre grounds are landscaped with water features.

A security room monitors cameras that cover the underground driveway and car park as well as the entire house. The Bishop's Avenue has a reputation for eclectic designs and questionable taste.

Architecture writer Gavin Stamp said: "Once upon a time the rich man was content with Stockbrokers' Tudor. Modern money must declare itself. The aim now is something like a plantation house in America's Old South with a huge two-storey portico, which can look like something ordered from a catalogue and stuck on."

Trevor Abrahamson of Glentree Estates, who is involved in most sales and lettings on The Bishop's Avenue, including Toprak Mansion, said: "The Bishop's Avenue is the honey pot all the rich bees fly to." One buyer who can almost certainly be ruled out is steel magnate Lakshmi Mittal.

The wealthiest man in Britain already owns London's most expensive house, the former embassy buildings at Kensington Palace Gardens which he bought from Bernie Ecclestone last year for around £60 million. He also already owns a palatial property on The Bishop's Avenue.

One possible hindrance to potential buyers is the next door derelict house, whose owner is trying to get planning permission to knock it down and build 14 flats.