Forbes: Gabe Newell a billionaire

Valve co-founder Gabe Newell is worth $1.5 billion (£954.5m), according to US magazine Forbes.

Newell, 49, makes his debut on Forbes' annual list of billionaires, with the magazine consulting industry insiders, analysts and investment bankers to calculate his net worth because Valve, a privately held company, does not publish its finances.

With Valve estimated to be worth at least $3 billion, and Newell holding a stake of more than 50 per cent in the company, his net worth is believed to be at least $1.5 billion. Valve's chief source of revenue is Steam, the PC distribution service that boasts 40 million registered users and controls an estimated 70 per cent of the PC download market.

Now in its 25th year, the Forbes list this year containts a record 1,226 names, worth a combined $4.6 trillion, of whom 128, like Newell, are new additions in 2012.