Margaret Thatcher implemented policies.
 Believing that the single market would result in political integration, Thatcher's opposition to further European integration became more pronounced during her premiership and particularly after her third government in 1987
Thatcher had been firmly opposed to British membership of the Exchange Rate Mechanism (ERM, a precursor to European Economic and Monetary Union), believing that it would constrain the British economy, despite the urging of both Chancellor of the Exchequer Nigel Lawson and Foreign Secretary Geoffrey Howe; in October 1990 she was persuaded by John Major, Lawson's successor as Chancellor, to join the ERM at what proved to be too high a rate

