The Aldermaston Marches
The Ban the Bomb movement in the 1950s may not be well known but 90% of people will be aware of its symbol which is now used everywhere for peace and anti-war protest. It was designed by a man called Gerald Holtom in the 50s and is now used around the world from the USA to Asia promoting peace and an end to conflict.
The Aldermaston Marches took place for several years starting (I think) in 1958. They started at the UK's nuclear research establishment at Aldermaston and ended in Trafalgar Square. Many very prominent intellectuals participated including Betrand Russell.
TPB Note: I was a student at the time and was involved in the marches in 1959 and 1960 (I think). I am reminded of those days whenever I see the 'Peace Sign' which most younger people associate with the Anti-War movement against the US involvement in Vietnam.