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Fitzrovia is one of the fastest changing parts of London. Tatty old warehouses, mews houses, and Sixties blocks once involved in the rag trade, full of grit and life, have been steadily converting to posh apartment blocks. For this once flea-bitten remnant of Georgian London is just five minutes from Oxford Circus.

In one such mews in 2013, Simon and Geraldine Tate spotted an 18th-century four-storey brick double warehouse with loading bays and an old hoist. It was being used as offices, its roof void had been opened to the fine, stout beams of its pitched roof, and it was fairly sound.

Since Simon and Geraldine’s children, Alexandra, 28, and Joshua, 27, had just flown the coop, the couple, in their mid-fifties, were looking for a flat in London. They grew up in Market Harborough, Leicestershire, and went to the same school. Soon after schooldays were over they started going out together. Simon, then a printer/publisher, moved to a flat in Putney with his older brother, and Geraldine, who’d joined the Civil Service, visited. They married in 1985.

“We loved doing up old buildings from the start,” says Geraldine. “Simon would come back from work and start hanging wallpaper, with me holding the ladder.”

Atmospheric: the six-flat development in a Fitzrovia mews (Charles Hosea)

They moved out of London to raise their family, first to a 14th-century mill in Chalfont St Giles, Buckinghamshire, which was in the Domesday Book — a project if there ever was one. Next, they converted a row of Victorian cottages into a family home. But once alone again, the lure of London proved too strong.

Simon now runs a small development company with his business partner Gareth Wilkinson, converting old buildings to residential. “Gareth and I were simultaneously looking for a building to develop,” says Simon, “so we thought, why not combine the two projects?”

Chatting with agents, Simon got wind of the double warehouse, which wasn’t yet for sale, contacted the owner, and bought it without it ever going to market. Not for a song — those days are over — but it had planning permission for six apartments which included digging out the basement. Simon’s brother Andrew, an architect, started on the drawings.

Sharing an eye for design: Simon and Geraldine Tate in their ultra-modern kitchen (Charles Hosea)

They were going to do six flats — duplexes in the basement, cleverly using borrowed light with a double-height lightwell at the front, and good, high ceilings, plus three flats to sell off-plan, and their own home at the top, enjoying the exposed rafters.

To bring light into the flats at the back, they negotiated with neighbouring properties to buy a narrow strip of land. “Getting 12 people to agree a price is like herding sheep,” Simon grins. It took six months, but meant they could put windows and skylights in, making a huge difference in light, especially in the two basement duplexes. Westminster planners have a keen eye, and requested small tweaks to avoid overlooking, but there were no objections, and they got cracking with the build in January last year.

It takes guts to do a job like this. Old buildings can and do throw up surprises, and excavating more than 13 feet down was almost a disaster. The substantial building was carefully acro-propped and all was going well, when one teatime a visiting utility company hit a water main. Water started spewing towards the excavation. Simon and Gareth knew that if it flooded the hole, it could wash out the props and collapse the entire building. Pumps arrived in the nick of time, Gareth stayed overnight, and a crisis was averted. The next day was business as usual.

All the flats are a good size with good light. The basements get light from east and west, with skylights over the kitchen areas. One has a smart glazed dressing room off the master bedroom.

Loading bay doors and side-sliding window sashes were rebuilt in double-glazed timber. Inside, all the flats have bespoke warehouse-style Crittall glazed doors to maximise light. The same smart ceramic tiles are in all the bathrooms, either black or off-white, and the lighting works well. Three flats sold off-plan in April this year, and the couple moved into their flat in June.

Geraldine is the company’s interior designer. In the couple’s home the soaring beams, painted off-white, look terrific, enhanced by a chandelier. The floors are limewashed oak, and the exposed wall on one side has original mellow tints and lime mortar.

The ultra-modern kitchen appears to have just landed in the living space. The sink area is in a double cupboard you can close; the central island with its black granite top and three stylish lights doesn’t overpower the room.

Geraldine explains: “We don’t put anything in a flat that we wouldn’t want ourselves.” Their coffee table is a 17th-century French door with enormous iron clouts in its top that they hauled back from France.

“In the country we cook, but it’s an urban village here,” she adds. “We love exploring and have eaten out every night. We still haven’t used the cooker. We’ve been here three months and it still feels like being on holiday.”

WHAT IT COST

Double warehouse with planning permission for six flats: £5.4 million

Total development cost: £2.5 million.

The value of the scheme now is estimated at £10 million

Two duplexes are for sale from award-winning TAG Urban Properties

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