pbr Tens of thousands of runners including a Princess and an assortment of celebrities gathered in the pouring rain for the start of the London Marathon.br ppbr Up to 36,000 athletes were expected to finish the 26.2-mile course after pounding through the streets of the capital to earn their marathon medals and raise money for countless charities.br ppbr At the start line celebrity chef Gordon Ramsay, running his 11th marathon in 11 years, said he was "nervous and excited".br ppbr GMTV presenter Lorraine Kelly said: "I'm really nervous about it. I'm just going to do my best. I'm determined to do it so fingers crossed. I don't know how long it will take. I'm just hoping to get around."br ppbr Princess Beatrice, 21, is aiming to become the first royal to complete the route as she joins a "human caterpillar" of 34 runners.br ppbr The team will be strung together two by two with bungee cords in an attempt to beat the record for the most people to finish a marathon while tied together.br ppbr The caterpillar is headed up by Virgin boss Sir Richard Branson's children, Holly and Sam. And this year Virgin has taken over sponsorship of the event for the first time.