A plane performing an aerobatic display nosedived towards the ground and nearly crashed after a loose pen in the cockpit jammed the controls, an investigation has found.

The vintage single-engine ‘Chipmunk’ aircraft was performing an aileron roll at 600 ft when the controls stopped working properly and it plummeted to just 50ft above the ground.

Only by vigorously pushing the pedals in the cockpit was 49-year-old pilot Paul Green able to regain control of the plane and perform an emergency landing.

A report into the incident, which took place last September close to White Waltham Airfield in Berkshire, has concluded that a partially crushed pen found in the fuselage had probably become lodged in the in the rudder control circuit, causing the 65-year-old DHC-1 Chipmunk 22 to plunge towards the ground.

The Air Accident Investigation Branch said: “During an aerobatic display the aircraft failed to respond to the pilot’s control inputs due to a restriction in the rudder control circuit caused by a loose article.

“The pilot reduced power and declared a MAYDAY.

"A detailed inspection of the aircraft completed a few days after the event confirmed that there were no defects with the flying controls. However, a partially crushed pen was found within the fuselage.