Women's Roller Derby is one of the fastest growing sports in London.
Demand is so great among new players eager to sign up that there's a year-long waiting list.
Wendy Hurrell finds out what it takes, as London's teams prepare to take on the US, in the North American League.
What is Roller Derby?
is an American contact sport based on formation roller skating around an oval track involving two teams.
Points are scored as the designated scoring player (the "jammer") of each team laps members of the opposing team, including its "blockers".