In his former office at Google, overlooking the San Francisco waterfront, John Hanke kept the shelves well stocked with games. Computer games, obviously befitting a man obsessed with technology, but proper old-fashioned board games too.

Prominent among them were Risk, Settlers of Catan and Stratego. All three have the same simple aim: to take over the world.

Today the 49-year-old floppy-haired Hanke can lean back in his new office chair a few blocks down along the city's Embarcadero and put his feet up. With the help of a small group of visionaries that includes a Japanese computer game wizard and a British advertising guru, Hanke's digital start-up Niantic has given the world the phenomenon that is Pokemon GO. Global domination is complete.

Briefly, for those few readers still unfamiliar with the smartphone game, Pokemon GO involves users walking around streets chasing and capturing cartoon monsters that appear in real locations on their phones. In the first week of release it became the fastest-growing mobile game of all time, and has now hit more than 30 million downloads. Nintendo, the Japanese-based game maker which has an unquantified stake in Niantic and owns one third of The Pokemon Company, has seen its market value more than double in a single week.