The demonstration, organised by the Campaign for Nuclear Disarmament in London's Trafalgar Square, was timed to mark exactly 50 years after the first atomic explosion in the New Mexico desert at 1.29 pm, July 16, 1945. Three weeks later 200,000 people died when the Allies dropped nuclear bombs on Hiroshima and Nagasaki.
The sombre atmosphere of the die-in - in the shape of a CND symbol - was enhanced by the tolling of bells 50 times at nearby St Martin-in- the-Fields.
Spurred into action by the French government's decision to resume nuclear testing in the South Pacific, CND campaigners from all over the country filled the square.
Speakers included two survivors from Hiroshima and Nagasaki, Masao Morihara and Reiko Yamada, CND vice-president Bruce Kent and MP Lynne Jones.