A bicycle used by Pippa Middleton to ride 500 miles (805km) through the United States is being auctioned off for charity.

The signed £2,500 custom-made Dassi Aero 6.2 road bike which the Duchess of Cambridge's sister rode to raise money for the British Heart Foundation is for sale on the charity's eBay site.

Miss Middleton, a BHF ambassador, has raised £20,000 in donations after taking part in the 3,000-mile (4,828km) relay Race Across America. Bids on the bike auction so far stand at £2,510.

Miss Middleton said: "The challenge of riding across the Rockies, coping with the heat of the Arizona desert and climbing over 170,000 vertical feet in the six days was incredibly tough, but every inch of the 3,000-mile race was worth it, to help the BHF fight heart disease."

Half the funds raised from the auction will be donated to the Michael Matthews Foundation which helps to provide education to children all over the world, which Miss Middleton also supports.

The auction runs until 9am on August 13 at www.bhf.org.uk/ebay.