You don’t see many flats priced at £1.5m on Gumtree.com. Tucked amid the secondhand sofa beds, pleas for a good cleaner and offers of house shares that make up the majority of postings on the website, there are always a few properties for sale, but they tend to be more modestly priced.

Yet when Simon Crookall came to sell his 2,000 sq ft, two-bedroom former warehouse a stone’s throw from Tower Bridge, he automatically thought of Gumtree. Why? He founded the website. “The response wasn’t huge,” he admits. “But it was one of the first things I did.”

Crookall, 40, set up Gumtree with his business partner Michael Pennington in 2000. Aimed largely at London’s itinerant Australian/New Zealander/South African population, it was an instant success when it went live, challenging Loot, which had hitherto dominated the market. As Pennington and Crookall had hoped, news of the site spread virally, through the pubs, clubs and bars frequented by new arrivals in the capital.

Soon, anyone from the southern hemisphere who had pitched up with nowhere to live, no furniture and no job was logging on to Gumtree in search of all three – and plenty of other Londoners began to follow their example.

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Two years ago, Crookall and Pennington sold up to eBay for an undisclosed sum, and are now working on Slando.com, a site that offers a similar advertising service to people in central and eastern Europe.

Now, Crookall is selling the flat that helped fund his success: he bought the property in 1996 for £130,000 in cash, but then mortgaged to help fund Gumtree in its early, uncertain days when it had eaten it’s founders’ savings.

He is sad to go. But as well as giving birth to a company, Crookall has also recently fathered a daughter, and now he, his wife Nealum, 36, and Myla, four months, need a more family-friendly home. The bachelor pad he created with the help of two architect friends back when he was a young single City boy is up for grabs.

Walking into the flat on a cold and grey winter day, you can feel your spirits lift at the amount of light that manages to stream in through the factory windows that line one wall. Exposed wooden floorboards stretch the length of the space, which is bisected by a curved wall at one end.

The rest of the living space is filled with a minimum of furniture – three sofas in a horseshoe shape at one end, a glass dining table to seat eight and a sculptural bookcase in a dramatic swirl that takes up an entire wall. A sleek stainless-steel and wood-topped kitchen at the left-hand side of the room looks suitably professional (Crookall is a keen cook), while hidden behind the curved wall are a bathroom and two bedrooms – one with openings at either end into the living space, the other divided off by a door, but with its own ensuite that sits behind a single wall at the end of the bedroom.

With only four doors in the whole property (into the master bedroom, the bathroom, a utility room and a storage area), the rest of the space is completely open plan – good for parties, but not so great for babies.

Originally a tannery, the building had been used as a furniture warehouse and was without walls, electricity and water (except for what was leaking into the building) when Crookall appeared on the scene.

“It was an empty mess,” he says. “But it was a blank canvas.” So, with the help of two recently graduated architect friends, Alex Mowat and Diana Cochrane, who went on to set up a practice called Urban Salon, he set to work. The project took about a year (it ran overtime) and cost £70,000. But it was ideal for a City boy who wanted to walk to work in 10 minutes, loved to party and had the opportunity to design his own bespoke living space.

“Alex and Diana were very enthusiastic,” says Crookall. “They sat me down, talked to me about my lifestyle and designed it from there” – hence the smart kitchen, the lack of walls and the minimalist feel. The property has stood the test of time well – the only interior change needed over more than a decade has been the odd lick of paint here and there – and, with lateral space all the rage in the capital today, the flat still looks fresh.

“I’ve been very happy here,” says Crookall, who is reluctant to leave. But family life beckons – he and Nealum, whom he married two years ago, have bought a Georgian house on the Isle of Man, where Crookall was born and where his family lives, which they are doing up and hope will be ready by early next year.

“It’s a great place to bring up kids – it’s safe and pollution-free,” says Crookall. “And it only takes two hours to get there, flying from City airport.” There are the tax benefits, too: Crookall is already domiciled in the Isle of Man, and will soon become a resident, thus benefiting from the low income-tax rates and absence of both capital gains and inheritance tax.

In the meantime, the couple and their daughter, Myla, are living in a three-bedroom flat in nearby St Katharine Docks, which they bought in August for £2.45m. Eventually, they plan to split their time between London and Man, where Crookall will join the family stockbroking firm.

And what of the flat? Crookall hopes for a buyer not unlike himself 10 years ago. “It’ll be someone young, who likes partying and wants proximity to the City,” he declares. Whether they will find the property for sale through Gumtree remains to be seen.

The flat at 172 Tower Bridge Road is for sale through Chesterton for £1.495m; 020 7357 7999, www.chesterton.co.uk

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