UK game and tools company NaturalMotion has raised $11 million to fuel its expansion into free-to-play mobile games.

The Series B round came from US outfit Benchmark Capital, which is an investor in location-based mobile developer Red Robot Labs and HTML5 platform Game Closure.

It was also a key investor in free-to-play online developer Riot Games, sold to Chinese publisher Tencent for an undisclosed sum rumoured to be around $400 million.

Benchmark partner Mitch Lasky, who previously ran EA Mobile and handled the Riot Games deal, will join the company's board.

Faster, better

NaturalMotion will use the cash to build up its internal development teams, notably its new office in San Francisco.

"We believe that users want rich, believable experiences on their mobile phones and tablets," said Torsten Reil, NaturalMotion's CEO.

"Just as animated movies have moved from Snow White to Toy Story, mobile games are moving from 2D farming games to high quality 3D experiences. These games connect with users on a deeper level.

"We are excited to partner with Mitch and the Benchmark team to build the leading publisher in this space."

NaturalMotion previously raised $8 million from Balderton Capital (previous Benchmark Capital Europe) in 2006, back when it was focused on its middleware animation tools business.

Its first mobile games were paid titles such as Backbreaker Football, but in 2011 it switched to the free-to-play model.

Its iOS social equine simulator My Horse has been particularly successful with millions of downloads, while its forthcoming title CSR Racing was the only game in Apple's WWDC 2012 keynote.

[source: NaturalMotion]