51st (London) Heavy Anti-Aircraft Regiment, Royal Artillery  51st (London) Heavy Anti-Aircraft Regiment was a volunteer air defence unit of Britain's Territorial Army from 1922 until 1955. During World War II it served in Norway, The Blitz, North Africa (when detachments defended Crete and Tobruk), and finally in Italy until the end of the war in Europe, by which time a proportion of the regiment's personnel were African soldiers, and the guns were engaging ground targets rather than aircraft. German air raids by Zeppelin airships and Gotha bombers on London and other British cities during World War I had shown the need for strong anti-aircraft (AA) defences in any future war. When the Territorial Army (TA) was reformed in 1922 it included a number of dedicated AA units. The senior of these was 51st (London) Anti-Aircraft Brigade, Royal Field Artillery (RFA), formed on 12 August 1922 at the Duke of York's Headquarters in Chelsea, London with 151st, 152nd and 153rd (London) AA Batteries. On 8 February 1923 it was transferred to the Royal Garrison Artillery (RGA), which had provided the AA batteries in World War I. However, on 1 June 1924 the RGA and RFA merged to become simply the Royal Artillery (RA). The regiment formed part of 26th (London) Air Defence Brigade also headquartered at the Duke of York's Headquarters. The original TA AA units were formed on a low peacetime establishment with a few old 3-inch guns on static mounts. As Britain's AA defences expanded during the 1930s, higher formations became necessary, and the 26th AD Bde (now renamed 26th (London) AA Group), including 51st AA Bde, was assigned to 1st AA Division organised to cover London and the Home Counties. On 1 January 1939 the RA replaced its traditional unit designation 'Brigade' by the modern 'Regiment', and the 'AA Groups' reverted to the more usual formation title of 'Brigades'. Anti-Aircraft Command was formed in April 1939 to control all the TA's AA units and formations. Duncan Sandys, MP, (son-in-law of Winston Churchill) was commissioned as a 2nd Lieutenant in 151st Bty in 1937. In 1938 he raised issues in the House of Commons about national defence based on knowledge he had gained from his TA service. He was warned that he risked prosecution under the Official Secrets Act, but the Committee of Privileges ruled that disclosure to Parliament were not subject to the Act.