Think of a sector ripe for an entrepreneur, and law is probably not top of your list. It’s highly competitive – there were 10,202 private practice firms operating in 2011, according to the Law Society – and a complex set of regulations makes applying new business models highly technical.

How also to combine the character of the law practice with that of the start-up? It’s a paradox that meets in the person of James Knight, managing partner of Keystone Law. A self-described "unusual person", he left his career as a lawyer to set up a business – a law firm.

Knight agrees that it’s not easy to be a legal entrepreneur. "Think of all the qualities you’d attribute to an entrepreneur: a degree of recklessness, a commitment to taking risks, perhaps a lack of attention to detail or following the rules. You won’t find any of these in your lawyer."

Indeed, as a provider of legal services, Keystone can’t take risks. "You have to structure your business so that it always follows the rules." Finding a niche in an established, regulated market wasn’t easy.

Knight’s new concept was the dispersed law firm. But the model is, in many ways, highly traditional. Lawyers act as lawyers, have their own clients, and perform ordinary legal work. The difference is that Keystone is little more than a central hub, with no expensive offices or teams of juniors. The lawyers work through the Keystone brand from their own homes or from serviced offices, and an IT platform connects them to one another. "It’s the place that the lawyers find all the administration of the firm," explains Knight. The small central office – essentially just a suite of meeting rooms and a small staff of administrators – also coordinates the work of its lawyers.

Knight came up with the idea in 2002, when working as a consulting lawyer. "Sometimes I’d run out of work, and I thought there must be an agency that caters to people like myself. But there wasn’t."

The benefits to him were clear. Lawyers could get on with what they enjoy – law – while outsourcing all the paperwork to the central administrators. Clients wouldn’t receive a pared-down service. But the model would combine the benefits of a full-service law firm with low-cost efficiency. Individual lawyers can pass around work (with a commission) to others in the Keystone network.

It’s a service, Knight says, that fellow entrepreneurs find appealing. "We don’t market on cost," he says, but smaller firms "like the firm, the lack of waste and duplication. They see a mirror of themselves."

Knight and his partner Charles Stringer self-funded the start-up, but not entirely out of necessity. "Keystone has had to grow organically," says Knight, and he sees this as part of its strength. For him, a personal investment is the best way to grow a business. "It teaches you a lot of the skills you need about not wasting time or money. It means you don’t go too far, too fast."

The first few years were hard. Honing the technology was "18 months’ of difficulty", and there was no one to copy or to turn to for advice when Knight was considering how the model would practically work.

And although he now talks of the importance of consistency – Keystone has the same address and telephone numbers as at its formation – it’s clear that some things had to be changed. "What advice would I give to an aspiring entrepreneur? Choose a good name." He alludes to his firm’s previous incarnation, Lawyers Direct, which was judged to sound "too ambulance-chasing." In its first year, the firm only turned over £90,000 – on the back of 10 lawyers’ work.

But, with a combination of ambition and humility (Knight is clear that, whatever Keystone’s size, it will only ever be a medium-sized law firm), Keystone is continuing to expand. "Lawyers like to work for us," says Knight. "It’s a very realistic alternative to a conventional firm."

CV JAMES KNIGHTCompany name: Keystone Law

Founded: 2002

Number of staff: 120

Turnover: £11m

Job title: Managing partner

Age: 45

Born: Cuckfield, West Sussex

Lives: London

Studied: Law

Drinking: Aberlour scotch whisky

Talents: Picking the right people and making deals

Reading: Wolf of Wall Street, by Jordan Belfort

Favourite business book: Forbes Greatest Business Stories of All Time, by Daniel Gross

Motto: "Make sure you pick the right people"

Hero: Sir Ranulph Twisleton-Wykeham-Fiennes, the adventurer who was the first person to completely cross Antarctica on foot

Awards: Entrepreneurial Law Firm of the Year, 2010