Current Tory policy chief Oliver Letwin urged Thatcher to press ahead with the viciously iniquitous poll tax in the 1980s despite warnings from leading ministers that it would be politically “catastrophic,” newly released documents reveal.

Papers released by the National Archives in Kew show that Mr Letwin — then an adviser in the No 10 policy unit — helped to convince the prime minister to use Scotland as a testing ground for the new tax.

Chancellor Nigel Lawson was one of those opposed to the introduction, warning that the whole scheme would be “completely unworkable and politically catastrophic.”