The United Kingdom is a charter member of the United Nations and one of five permanent members of the UN Security Council.
United Kingdom's role in establishing the UN 
The term "United Nations" was suggested by Franklin D. Roosevelt to Winston Churchill during World War II, to refer to the Allies. It appeared in the Declaration by the United Nations where, on 1 January 1942, 26 nations pledged to continue fighting the Axis powers.
Veto power in the UN Security Council 
The United Kingdom used its Security Council veto power, along with France, to veto a draft resolution aimed at resolving the Suez Canal crisis in 1956. They eventually withdrew after the U.S. instigated an 'emergency special session' of the General Assembly, under the terms of the "Uniting for Peace" resolution, which led to the establishment of the United Nations Emergency Force I (UNEF I), by the adoption of Assembly resolution 1001 . The UK also used the veto unilaterally seven times because of Rhodesia.
See also