Active from 1922 – 1961 the 53rd (City of London) Heavy Anti-Aircraft Regiment, Royal Artillery was a volunteer air defence unit of Britain's Territorial Army.
During World War II the regiment was embodied on 5th August 1939 and occupied gun positions in parks and open ground around London. Thus, the regiment was fully deployed when war was declared on 3rd September.
The Regiment fought in the Battle of France and The Blitz, and later served in India, where it was converted to Medium Artillery. Post-war it reverted to the AA artillery role.