In September 1956 just before the Suez Crisis. French Prime Minister Guy Mollet met up with British Prime Minister Anthony Eden in London. Mollet proposed a union between the United Kingdom and the French Union with Elizabeth II as head of state and a common citizenship. As an alternative, Mollet proposed that France join the Commonwealth. British Prime Minister Anthony Eden rejected both proposals and France went on to join the Treaty of Rome, which established the European Economic Community and strengthened the Franco-German cooperation.
But what if Eden accepted Mollet's first offer? What if this would lead to a major global power known as the Franco-British Union.
As Britain and France decided to stick together, the Suez War ended in British/French\Israeli victory. Following the end war the Governments of the United Kingdom and France started to hold serious talks of a possible merger between the two countries. The Treaty of Cherbourg was signed in June 1957 which stated that: France and Great Britain shall no longer be two nations, but one Franco-British Union. The constitution of the Union will provide for joint organs of defence, foreign, financial and economic policies. Every citizen of France will enjoy immediately citizenship of Great Britain, every British subject will become a citizen of France..
On the 1st September 1957, The constitution of the Union was passed through the British and French Parliaments officially creating the union with elections to the Union Parliament happening the following month.
BBC News Report on the Union - When Britain and France nearly married