A spokeswoman for Thorpe Park said: "We stopped the ride because a guest ignored our ride restrictions and put their leg outside of the cart while on board Colossus which was spotted by our vigilant staff on CCTV.
"Therefore we stopped the ride as soon as possible and evacuated all guests.
"Colossus is back up and running.
"All guests must keep their arms and legs inside the cart at all times when riding our rollercoasters."