Both were based at the Duke of York's Headquarters in Chelsea, where the units of the 2nd AD Bde were accommodated in buildings used before the First World War by King Edward's Horse and the Royal Army Service Corps divisional train of the 47th (1/2nd London) Division.

Meanwhile, 3rd AD Bde's units were based at Lytton Grove, Putney, taking over pre-war buildings previously used by the City of London Yeomanry (Rough Riders).

1st AA Division was formed in 1935 at RAF Uxbridge to command the growing number of Territorial Army (TA) anti-aircraft gun and searchlight units covering London and the Home Counties.

[6][7][8][9] The AA Groups took the more usual formation title of Brigades on 1 January 1939 after the Royal Artillery replaced its traditional unit designation 'Brigade' by the modern 'Regiment'.

Because the units possessed only a small scale of transport, elaborate plans had been made to requisition civilian vehicles, ranging from heavy lorries to buses and private cars.

[12][13] During this period of tension the Territorial Army grew enormously, and existing TA infantry battalions continued to be converted to AA regiments.

[14] The further deterioration in international relations during 1939 led to a partial mobilisation in June, and a proportion of TA AA units manned their war stations under a rotation system known as 'Couverture'.

[15] Just before the outbreak of war, 26 AA Bde moved its headquarters to Brompton Road in South Kensington, where a Piccadilly line underground railway station had been disused since 1934.

1st AA Division established a control centre at Brompton Road, where the tunnels, subways and lift-shafts were adapted to provide bomb-proof accommodation for a Central Operation Room reporting direct to HQ No.

11 Group RAF at Uxbridge, and four Gun Operations Rooms (GORs) subdividing the London Inner Artillery Zone (IAZ).

An elaborate network of dedicated telephone lines was laid by the General Post Office and Royal Corps of Signals, linking the AA sites, including many isolated searchlight positions.

[10] While the Luftwaffe attacked RAF airfields in south east England during the Battle of Britain, 26 AA Bde was hardly involved, but on 2 September 1940 a raid up the Thames Estuary reached the edge of the London IAZ and was engaged by guns of the brigade.

111th HAA Regiment (347, 355, 356 and 389 Btys) joined early in 1943, but left in May 1943 to go to GHQ Reserve, later 21st Army Group, preparing for the invasion of Normandy (Operation Overlord).

Defences had been planned against this new form of attack (Operation Diver), but it presented a severe problem for AA guns, and after two weeks' experience AA Command carried out a major reorganisation, stripping guns from the London IAZ and other parts of the UK and repositioning them along the South Coast to target V-1s coming in over the English Channel, where a 'downed' V-1 would cause no damage.