You accepted the organiser's terms and conditions:

I declare that the above named person is physically fit to take part in the event. I understand that they participate entirely at their own risk, and relieve the race referee, the race organisers / personnel, of any responsibility for injury, loss or damage sustained to either their person or property as a result howsoever caused. I also declare that the above named person's cycle will be in a roadworthy condition for the race and that they have agreed to abide by the rules of British Triathlon.