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The online-only sale – the third and final part in a trilogy of auctions held as part of the arrangements following her death in 2013 – attracted bidders from 36 countries.

Comprising 170 lots relating to her time in office with estimates ranging from £100-15,000, the top lot was a multi-gem and diamond Van Cleef & Arpels brooch.

Estimated at £10,000-15,000 it was hammered down at £40,000 (£50,000 with premium).

Adrian Hume-Sayer, director and specialist for private collections at Christie’s, said: “The result of this final auction in the series of sales held at Christie’s following Mrs Thatcher’s death in 2013 illustrates the enduring interest in the United Kingdom’s longest serving 20th century prime minister.”

In 2015 the separate auctions achieved a premium-inclusive £4.5m.

Also last week, an archive of Harold Wilson (1916-95) and his wife Mary sold at Hansons. Described by Hansons’ valuer Jim Spencer as a “50,000-piece jigsaw puzzle”, the sale encompassed letters, photos and memorabilia from Wilson’s times in office with reminders of his connections with the rich and famous of his day.

In March it was announced the archive of Labour’s longest-serving MP Tony Benn (1925-2014) had been accepted by the British Library. Benn kept a diary from the age of nine and the archive begins from there and spans his political career including a substantial collection of source material that reflects the history of the UK during his lifetime.

Christie’s assisted in the negotiation leading to the archive being accepted by the nation in lieu of inheritance tax to settle £210,000 of tax. It will be permanently allocated to the British Library, in accordance with the condition attached to its offer.