During early 1940, two Bellman hangars were constructed and as the Battle of Britain started in August a Civilian Repair Organisation operated by Rolls-Royce was established to repair battle-damaged Hurricanes. The organisation also converted 100 Hurricanes to Mark II standard by installing the Rolls-Royce Merlin XX engine. A further conversion programme installed the Merlin 45 into the first Supermarine Spitfire Mk.Vs, and later approximately 300 Spitfire Vs were converted to Mk.IXs. The ferrying of repaired or modified aircraft was the responsibility of No. 1 (RAF) Ferry Pilots Pool and the Air Transport Auxiliary (ATA).