Accession of the United Kingdom to the European Communities

The Accession of the United Kingdom to the European Communities (EC) which was the collective term for the European Coal and Steel Community (ECSC), the European Economic Community (EEC) and the European Atomic Energy Community (EAEC) took effect on 1 January 1973, after the ratification of the Accession treaty which was signed in Brussels on 22 January 1972 by the then Conservative Prime Minister Edward Heath who had pursued the UK's application to the EEC since the late 1950s. Denmark and Ireland also joined as part of the same expansion but Norway, who had signed the same treaty, declined to ratify it and so it was amended to exclude them. The ECSC and EEC would later be integrated into the European Union under both the Maastricht and Lisbon treaties.

The UK had first applied to join back in 1961 but this was vetoed by French President Charles de Gaulle. The UK's negotiation team in 1970–72 included Con O'Neill and David Hannay.

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