Celebrities don their bras to prepare for the Moonwalk

Celebrities are donning their bras and joining thousands of people at midnight in a London park for a charity walking marathon.

The Moonwalk, which starts in Battersea Park, is aiming to raise �4m for breast cancer research and breast cancer care.

The organisers of the event, which began with 100 participants six years ago, say it will be the biggest ever with 15,000 participants.

Those taking part include TV presenter Lorraine Kelly and comedienne Victoria Wood.

The power walkers set off at midnight in either the 26.2-mile Moonwalk or the Half Moon, which is 13.1 miles.

The route starts and ends in Battersea Park going via Tower Bridge, Chelsea, Kensington and Hyde Park.

Since the event began in 1997, �6m has been raised for Breakthrough Breast Cancer and the Bristol Cancer Help Centre.