The six contestants were each given £500 to start the game. They participated in five rounds of 90 seconds duration each, and had to buzz in to answer questions read by the host. A correct answer entitled them to steal £50 from another player, but an incorrect answer forced them to give £50 to another player. In each case, they got to choose the player. From the fourth round onwards, the amount doubled to £100.
At the end of each round, the person with the least money was eliminated, and had to give all their money to another player. After the fourth round, however, the eliminated player could split their money between the two remaining players in whatever proportion they desired (although presumably had to keep it in multiples of £50).
When only one player remained, they then had to answer six questions correctly in 75 seconds to keep the £3000 they'd won. Failing to get six questions right meant that the £3000 had to be given to one of the previously eliminated players.