The Committee's first act of civil disobedience on 18 February 1961 was a sit-down demonstration at the Ministry of Defence in Whitehall, London, to coincide with the expected arrival of on the River Clyde. (Picture) Between 1,000 and 6,000 people took part. Somewhat to the surprise of the Committee, there were no arrests. At the next sit-down demonstration, on 29 April in Parliament Square, the police arrested 826 people. There were also marches and sit-downs against nuclear testing and demonstrations at the US and Soviet embassies in London and at the Polaris submarine base.