And they're off!
Pippa Middleton and her younger brother James set off on their epic cross-country trek from San Diego to Annapolis, Md., yesterday as part of the "Race across America".
They are part of a team which will attempt to bike coast to coast through 12 states in eight days.
Pippa and and her brother are part of a team of eight cyclists, and will be riding three hours a day each in relay.
Pip told the Mail: “I think every cyclist including me will be layering it on. Once we get going it’s non-stop, with very little sleep. It’s nerve-racking but exciting and all for a great cause.”