Promoted to the rank of air vice marshal, Park took command of No. 11 Group RAF, responsible for the fighter defence of London and southeast England, in April 1940. He organized fighter patrols over France during the Dunkirk evacuation and in the Battle of Britain his command took the brunt of the Luftwaffe's air attacks. Flying his personalised Hawker Hurricane around his fighter airfields during the battle, Park gained a reputation as a shrewd tactician with an astute grasp of strategic issues and as a popular "hands-on" commander. However, he became embroiled in an acrimonious dispute with ambitious Air Vice Marshal Trafford Leigh-Mallory, commander of 12 Group.