The pilot had been asked by his instructor to start the engine of G-MWOY prior to his arrival in preparation for an instructional session. The pilot strapped himself in the forward seat and commenced pulls of the starter cord: after only a few attempts the engine started and ran up to high power. The aircraft lurched forward, overpowering the foot brake and the pilot found he could not close the throttle. In addition his gloved hand could not operate the ignition switch in time to prevent the aircraft from striking G-CEGJ, which was unoccupied and parked about 8 m away. GJ was spun round and tipped onto its left wingtip whilst OY continued until it encountered a concrete sleeper bordering the car park, the nosewheel bounced over it but the aircraft was brought to a halt when the mainwheels contacted and the pilot finally managed to switch off the ignition.
The pilot reports that a kinked throttle cable, which he possibly damaged when he climbed into the aircraft, and a weak throttle return spring were probably responsible for the stuck throttle. He noted that everything had appeared normal when he had started the engine earlier in the day.