Revenue at the firm has grown 978% year-on-year. The ad technology firm produces highly complex algorithms that allow advertisers to target consumers with personalised online ads. In layman's terms: Struq flogs people stuff they'll definitely want to buy.
The return on investment for advertisers is mind-boggling - on average, for each pound spent, they get customers spending £9.93 with them. No wonder Barnett's been inundated with new clients. "Most of them have been fashion labels," he says. "It's funny how these things happen, but once one company signs up, all the companies in the same industry think: 'We should be doing this!'."
As of last month, names including Ted Baker, Lovefilm and French Connection use Barnett's online wizardry to boost sales.
Despite his success, Barnett is remarkably down to earth. Cautious to a fault, he has only just started paying himself and he still lives in a tiny flat in Bromley - "My staff live in much nicer houses than me," he laughs. Although he is moving into a new pad soon: "My wife has been living in a shoebox long enough," he says.
Obviously, money isn't a huge driver for Barnett. But what is? "Proof," he says. "When I was starting out, I was told by an entrepreneur that I really admired that I would never succeed. It filled me with a burning rage. It made me determined to succeed."
Barnett is full of surprises. He originally trained as a lawyer and was destined for a life of zero risk, maximum financial reward. "I hated it," he admits. "I always knew I had to start my own business."
His legal background has proved mighty useful at Struq, however. Rather than fork out huge sums in legal fees, Barnett looks over all the business contracts personally. Glen Calvert, sales director, hands Barnett a pint of Guinness. Barnett explains: "He owes me a drink. He's always signing documents and leaving them on my desk - and I have to sort out the legal mess!" Calvert laughs uproariously.
But Barnett's diligence and hard work have paid off. Struq is now worth double digit millions.The business has never borrowed money. It's grown organically from inception and has a nice wedge of cash in the bank.
On that note, Barnett excuses himself to go and play pool with the people who have helped make his business a success. And, as I wend my way through drizzly Soho, Barnett's parting comments ring in my ears: "This business is infinitely scalable. There's literally no limit to the growth we could achieve" and I wonder what crazy news Barnett will have to tell me next time we meet for a pint…