The teams set off from Greenwich. They must pass through five checkpoints to reach their final destination. First up: the ancient city of Delphi.

The five teams head to their next checkpoint - Baku in Azerbaijan - a journey that will see them leave behind the familiarity of the West for the exotic and unknown of the East.

The four remaining teams leave Azerbaijan and head across the deserts, mountains and Silk Road cities of Central Asia in the third leg of the challenge. Along the way, they meet a stuntman with a high-octane car, get the chance to watch a grisly 13th-century Kazakh sport played between horse riders and using the carcass of a dead goat, and brave a storm on the Caspian sea.

The global travel series reaches another level this week as the four remaining teams enter the People’s Republic of China. After nearly a month on the road together, relationships are coming under increasing pressure in what is the most challenging leg of the race to date. With vast distances to cover to the checkpoint - the ancient village of Huangyao - budgets are running low and emotions are high.

It is the penultimate leg of BBC Two’s unrivalled travel series, that has taken viewers on a journey through the wilds of Kazakhstan to ancient villages in China. This leg sees the remaining four teams head through the dense forests and bustling metropolises of Cambodia and Vietnam, and the final checkpoint before Singapore – the island paradise of Koh Rong.