Gamblers keen to get an edge over their rivals, have taken to employing "courtsiders", who send back live data to syndicates and betting companies while a game is under way. Last year a British man became the first person to be arrested while engaged in the practice, at the Australian Open tennis tournament. For Dan Dobson it was a dream job. Still only 22 years old, he got to travel the world with some friends, earn a decent salary and watch top-level tennis. He was not just a spectator though, he had to send back live data to the gambling syndicate he worked for, as each player scored a point. To do this he used a simple device hidden inside his shorts. "You would sit on court for as long as you were needed pressing the buttons, which were sewn into my trousers and relay the scores back to London. You'd press one for Djokovic, two for Murray, for example, as fast as you could," he says. He is affable with the insouciance of youth and the confidence that comes with being well over six-foot tall, head-and-shoulders above most people. Courtsiding is inextricably linked to "in-game" betting - gambling while an event is taking place. This betting happens on exchanges like Betfair, where gamblers pit themselves against one another, offering constantly changing odds on a player or team winning or losing, as a match progresses.