The brigade was formed on 28 September 1938 at Boston Lodge, South Ealing in West London, under the command of Brigadier O.W.

[15] After the intense period of activity against airfields during the Battle of Britain, the German Luftwaffe switched to night raids against London and other cities (The Blitz).

The cluster system was an attempt to improve the chances of picking up enemy bombers and keeping them illuminated for engagement by AA guns or RAF Night fighters.

[41] This formation in Southern and South-Eastern England was responsible for defending the assembly camps, depots and embarkation ports for the forthcoming Allied invasion of Normandy (Operation Overlord).

Meanwhile, 2 AA Group had to deal with a sharp increase in Luftwaffe air raids trying to reach London during the winter of 1943–4 (the so-called 'Little Blitz').

[49] The first V-1 missiles were fired against London in June, a week after D-Day, and Operation Diver was activated.

Firstly, mobile HAA guns were replaced with static installations that could traverse more quickly to track the fast-moving targets.

These were emplaced on temporary 'Pile platforms' named after the Commander-in-Chief of AA Command, Gen Sir Frederick 'Tim' Pile.

The whole process involved the movement of hundreds of guns and vehicles and thousands of servicemen and women, but a new 8-gun site could be established in 48 hours.

The guns were constantly in action, and the success rate against the 'Divers' steadily improved, until over 50 per cent of incoming missiles were destroyed by gunfire or fighter aircraft.

This phase of Operation Diver ended in September after the V-1 launch sites in Northern France had been overrun by 21st Army Group.

It was then rejoined in October and November by 128th and 136th HAA Rgts, and by 14th (West Lothian, Royal Scots) LAA Rgt.

In April 1946, these regiments were disbanded[44][57] and replaced in 40 AA Bde by the reformed 3rd and 5th HAA Rgts, which were Regular Army units that had been lost at the fall of Singapore and Hong Kong respectively in 1941–42.