Part One

Sue Barker hosts live coverage of one of the nation's biggest sporting events, the Flora London Marathon. The world's top long distance runners will be doing battle over 26.2 miles in the race, which is now in its 29th year. Reigning champion Martin Lel is defending his title and looking for a record fourth win. But the Kenyan faces stiff opposition from a top class field, which includes the gold, silver and bronze winners at last year's Beijing Olympics. With Paula Radcliffe ruled out with a broken toe, Britain's best hope lies with Mara Yamauchi, but also lining up in the women's event are defending champion Irina Mikitenko of Germany, Olympic gold medallist Constantina Dita of Romania and Kenyan world champion Catherine Ndereba.

Meanwhile, Britain's David Weir is looking for his fourth consecutive win in the men's wheelchair event and defending champion Sandra Graf of Germany heads the line-up for the women's equivalent, having broken the course record on her debut last year.

But the London Marathon is one of the rare sporting events where it's not just about the elite athletes. Around 35,000 runners will also be pounding the streets past some of the capital's most famous landmarks in a colourful and spectacular festival of running that raises millions each year for charity.