Pairs of contestants receive a modest starting pot of seed money comprising £250. As soon as they receive the cash the clock starts ticking and their mission is clear - double the money within the next exhilarating few hours or face elimination from the game. The stakes get higher until one team ultimately wins a life-changing £20,000. Those taking part include father-and-son Dale and Harvey, competitive publicans Cath and Lynn, and best friends Radhika and Seema.

Round two sees the remaining teams with three days to turn £500 into £1,000. As the clock starts, a battle of the lemonade brews - as one team tries to pedal a homemade recipe, while another upsells supermarket pop. Elsewhere, one duo charges £60 a head for a supper club event, another opts for a rowdy bingo night and a rival team attempts to throw a high-end party in an upmarket nightclub. When the clock stops, the teams return to The Vault to see who managed to double their money and kept their place in the competition.

Round 3 sees the remaining teams afforded one week to double £1,000. The twins host an event for local ladies in Leeds, while married couple Nissy and Ben offer a webinar on how to have a happy marriage. On Bournemouth beach, a father and son decide to run a hook-a-duck game, but at £5 a go they'll need a lot of customers to reach the £2,000 target. Best friends Radhika and Seema host an erotic art workshop on an industrial estate in north-west London for £75 per person, while in Telford, Dale and Harvey attempt to stage a talent show contest.