C5 owners began modifying their vehicles to achieve levels of performance far beyond anything envisaged by Sinclair. Adam Harper used one C5 as a stunt vehicle, driving it through a 70 ft (21 m) tunnel of fire,[1] and adapted another to run at 150 miles per hour (240 km/h), aiming to break a world land speed record for a three-wheeled electric vehicle and the British record for any type of electric vehicle.[93][94] He said later: "Up to 100 mph [160 km/h] it's like you're running on rails, it's really stable.