Princess Beatrice is the only royal to have completed the London Marathon, according to multiple reports. She ran the 2010 race in aid of her mother Sarah Ferguson's charity Children in Crisis. Beatrice was part of a group of 34 runners who formed a human caterpillar, all tied together. The group set a record for the greatest number of people to complete a marathon while bound together.
Prince William and Kate Middleton made a special appearance at the 2017 London Marathon. They cheered on competitors from a water station for the 'Heads Together' mental health charity. Some runners squirted the couple with water during the event.
Kate Middleton has expressed a desire to run the London Marathon but cannot due to security concerns, according to multiple reports. Sophie, Duchess of Edinburgh ran 1.5 miles of the 2020 London Marathon in torrential rain. She ran alongside Tomas, who was raising funds for Mencap, of which she is patron.
Princess Beatrice's finishing time in the 2010 marathon has not been disclosed. It is unclear if any other royal family member attempted the marathon but did not finish. The exact record set by Beatrice's group has not been specified.