Leigh-Mallory, the commander of the neighbouring No. 12 Group RAF (12 Group) to the north, was an advocate of a Big Wing policy, causing enormous friction in his relationship with Park. One of Leigh-Mallory's subordinates was the acting leader of No. 242 (Canadian) Squadron RAF (242 Squadron), Douglas Bader, who had flown in Park's Big Wings over Dunkirk a few weeks earlier. Experience covering the French beaches against air attack had convinced Bader that large formations were essential and with Leigh-Mallory's blessing, a wing was formed at RAF Duxford to try to prove the Big Wing theory. Supported by Duxford station commander Group Captain "Woody" Woodhall, Bader's wing theory was developed over the next few days and initially involved three squadrons; 242 Squadron, No. 310 (Czech) Squadron RAF (310 Squadron) flying Hawker Hurricanes and No. 19 Squadron RAF (19 Squadron), based at nearby RAF Fowlmere flying Supermarine Spitfires.