Hearthstone: how a game developer turned 30m people into card geeks

It was born as a niche project, but went on to become one of the biggest games of the decade. Here's part one of our inside story on Blizzard's big adventure

On the set of ITV's costume drama Mr Selfridge, in a quiet moment between takes, actor Greg Austin is a world away from his co-stars. Although dressed as an Edwardian gentlemen, he is glued to his iPhone, and to one game in particular. Hearthstone.

"I got into it somewhat late, about a year after its release," he says. "But since then I've been playing avidly. It is easy to learn, which means anyone can play it and enjoy themselves, but it is also difficult to master." Austin loves the game so much, he now has his own dedicated YouTube gaming channel, EuphAuric, posting regular Hearthstone videos.