Children learn about air defences on Empire Air Day at Hendon . Large crowds , including many children , watched the Empire Air Day display at Hendon Aerodrome . The 11th London Regiment ( The Finsbury Rifles ) , which now comprises the 170 and 171 Anto Aircraft Batteries , co-operated with the Royal Air Force in the display . Photo shows , children trying an anti aircraft listening post at Hendon . 23 May 1936 *** Local Caption ***