Jill Christie, a police officer from Brentford, pulled on a Supergirl fancy dress costume in order to set a world record on the streets of the capital.
She finished the race in an impressive time of three hours, eight minutes and 55 seconds in order to become the fastest ever woman marathon runner in a superhero costume.
Jill, who took part in the marathon to raise money for Crimestoppers, said wearing superhero fancy dress had proved to be a real advantage.
"I recommend dressing in a costume, even if you're not going for a record, because you get so much encouragement," she explained.
There were certainly plenty of people who agreed with her.
Hundreds of entrants wore fancy dress costumes, helping to raise substantial sums for charities.