Sporty Pippa Middleton is the only girl in an eight-person team who'll be aiming to complete a 3,000 mile charity bike race.
She set off yesterday with her brother James Middleton and will cycle across 12 states, leaving from Ocean Side, California to journey to Annapolis, Maryland for the Race Across America fundraiser.
The pair were dressed in patriotic sports tees and tops, bearing the British flag and a logo for their chosen charity - The British Heart Foundation, for whom Pippa was named an ambassador last week. She'll also be raising money for the Michael Matthews Foundation - named after a young Brit who died ascending Mount Everest.
The team will have to survive on very little sleep to complete the challenge within 12 days, and will ride in relays of five to six hours in groups of four, to leave time to sleep and eat.
The challenge has previously been completed by less than 200 people, and Pippa is one of few female competitors. But she told The Mail On Sunday, prior to the event, that she's "not worried" about sharing the team's sleeper camper van with all guys.
Race organiser, Rick Boethling backed Pippa up, saying: "Riders regularly hallucinate through lack of sleep. Pippa's a tough cookie"
This isn't the first extreme sporting event she's competed in for charity - she's previously completed an endurance ski race in Switzerland in 2012 and also participated in the Highland Cross in 2011.
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