The Big Wing contrasted with the tactics used by Air Vice-Marshal Keith Park, the commanding officer of Fighter Command's 11 Group. Park's tactic was to meet the raids with small groups of one or two squadrons, which he considered to be the most flexible and effective use of his aircraft. However, Leigh-Mallory, the commander of 12 Group, was a powerful advocate of the Big Wing policy, causing enormous friction in his working relationship with Park. Under Bader a special wing was formed at Duxford aerodrome to try and prove the Big Wing theory. Over a number of days in September 1940 the wing was sent up to try and disrupt the Luftwaffe raiders.
To this day there is controversy over the effectiveness of the wing. Leigh-Mallory and Bader claimed it was a great success, though post-war analysis suggests the actual number of German aircraft shot down by the wing was a fraction of those claimed. However, casualties for the Balbos were lower than in the smaller formations and benefited from protection in numbers.
Keith Park had experimented with wings and insisted they were unwieldy, difficult to maneuver into position, and rarely in the right place when needed. He also pointed out their use was inappropriate in 11 Group which was closer to the enemy than the Midlands-based 12 Group. The wings took a long time to form up and there was insufficient time available over Kent and Sussex to ready large formations to tackle the incoming raids. Bader countered by pointing out that his wing could be used as a reserve for 11 Group. Positioned well away from the Luftwaffe bases in France he could, if adequate early warning was given, be in-place at altitude when the wing was needed. However, 11 Group always asked for assistance too late, making it difficult for him to make a timely appearance.
The general view with hindsight is that the Big Wing's combat effectiveness was inflated by Leigh-Mallory and Bader and that Park's tactics (which included the occasional use of two- and three-squadron wings) were correct for the conditions he had to fight under. However, there's no doubt the Big Wing had a morale impact on the German aircrews, who were often told by their superiors how the RAF was down to its "last fifty Spitfires". The repeated appearance of the Bader wing soon put paid to that lie.
The clash of opinion between the 11 and 12 Group commanders was left unresolved by Leigh-Mallory and Park's commander, Air Chief Marshal Sir Hugh Dowding, commanding officer RAF Fighter Command. This was a crucial failure of leadership at a critical point in the battle. Relations became acrimonious, with Park demanding the Duxford squadrons be used to protect his 11 Group airfields while Leigh-Mallory insisted his Big Wing should be unleashed to deliver the Luftwaffe a knockout blow. Bader's tendency to freelance across southern England with his wing also added to the ill-feeling.
However, Trafford Leigh-Mallory had allies in the senior echelons of the RAF. Subsequent events, in which Dowding was removed from his post at Fighter Command and Leigh-Mallory promoted to command Keith Park's group have been blamed on the Big Wing controversy. However, in recent years the suggestion has been put forward that Big Wing was just one element in Dowding and Park's removal. Dowding's apparent inability to get to grips with the night bombing threat has been offered as a primary reason for his dismissal.
Big Wing made a last appearance as a defensive formation in paper exercises run by Leigh-Mallory as commander 11 Group in January 1941. The intention was to prove the superiority of large formations using the circumstances of an actual attack on Kenley, Biggin Hill and Hornchurch sectors on 6 September 1940. Leigh-Mallory completely mismanaged the operation, permitting the raid to progress unhindered and resulting in Kenley and Biggin Hill being 'bombed' while their aircraft were still on the ground. One of Park's former controllers explained Leigh-Mallory's mistakes to him. He replied that he would do better next time and that if a large-scale raid approached he would permit it to bomb its target and intercept it in force on its return to France. The enemy, he believed, would be so badly mauled that there would be no more raids.
Leigh-Mallory never got to use the Big Wing defensively. By this time it was mutating from a defensive into an offensive formation. Douglas Bader would eventually lead these new wings on massive fighter sweeps over France known as CIRCUS operations.