By Ronald Grover and Sue ZeidlerLOS ANGELES (Reuters) - William Hill, Britain's largest bookmaker, said on Thursday it has won approval from Nevada regulators to become the first British betting service to run a sports book in the state.The green light from the Nevada Gaming Commission allows the British firm to begin offering sports betting on mobile devices to bettors in Nevada, and positions the company to be among the first out the gate should legal restrictions on U.S. online gaming be lifted."Mobile gaming is the fastest growing part of our business, and this adds a new dimension for us," said William Hill chief executive Ralph Topping.Two years ago, he said, the company was taking in $1.5 million a week from mobile gamblers in the United Kingdom. Today, it handles $25 million a week.The London-based company, which says it has more than 2,370 betting parlors across Great Britain, entered the Nevada market in the spring of 2011 by agreeing to pay $55 million to acquire three sports gaming companies. It intends to continue to operate those as "brick-and-mortar" businesses.Approval of those deals were conditional on William Hill getting licensed by Nevada regulators. One of the companies, Brandywine Bookmaking, operates 17 sports books in Nevada and also runs the Delaware Sports Lottery with partner companies.With Nevada's approval, Topping said the company intends to make more acquisitions. It "had offers coming out of the woodwork" as it neared regulatory approval, he said.Online gambling provided 28 percent of William Hill's $1.7 billion, or about 1.1 billion pounds, in revenue last year, according to company filings.The company generated more than 90 percent of its net revenues in Britain last year but is seeking to expand internationally into regulated markets. It is one of a number of British companies granted licenses for online gaming in Spain.(Reporting By Ronald Grover; Editing by Bob Burgdorfer)