London: Pippa Middleton will brave sub-zero temperatures, along with her brother James, to take part in the world's longest cross-country ski race to raise money for needy children.

The Duchess of Cambridge's younger siblings will be among more than 15,000 skiers taking part in the Vasaloppet, a 56-mile ski marathon across Swedish mountains.

First run in 1922, the race is billed as a "unique test of individual courage and resources", reported a daily.

They have already been pledged more than 4,300 pounds in sponsorship, including a single 1,000 pound donation from one couple, although not Prince William and Duchess Kate.