A ring Margaret Thatcher wore the day she became the UK's first female Prime Minister and a library globe which stood in her office are among 170 of the Iron Lady's personal possessions going under the hammer next month.

Christie's is auctioning the lots in the Mrs Thatcher, Part III, online sale which opens for bidding between 2 and 9 May.

The auction coincides with the 40th anniversary of Margaret Thatcher's election as the UK's first female Prime Minister (1979-1990), and is the third and final part in a trilogy of auctions held as part of the arrangements following her death in 2013.

Comprising lots relating to Mrs Thatcher's time in office, personal possessions, jewellery, clothes and handbags, estimates range from £100 to £15,000.

Evocative items of note include her 'uniform' jewellery, comprising a hardstone bracelet and 18-carat gold and amethyst ring, gifts from her husband Denis, which were always worn alongside a pearl necklace.

The ring or bracelet were worn for almost all occasions, from the day Mrs Thatcher entered Number 10 Downing Street on 4 May 1979, to her historic meetings with global figures including Mikhail Gorbachev, Ronald Reagan and Nelson Mandela.

Other highlights include two evening ensembles by Camilla Milton - a blue outfit Mrs Thatcher wore to the dinner at 10 Downing Street to celebrate the HM Queen Elizabeth II's Golden Jubilee, attended by the Queen and all surviving Prime Ministers and a gold one she wore to the unveiling of her statue in the House of Commons.

The numerous other treasures include notes for Mrs. Thatcher's speeches and autobiography, a typed list of Prime Minister's Engagements from her final day in office, portraits, and even a library globe which stood her office.

The Margaret Thatcher sales began in 2015 when Part I and Part II attracted a global audience, with all lots sold and for a total of £4,516,038.

Part III will provide further public and private insights into the trajectory of a political titan and an opportunity for collectors from around the world to acquire property from the longest serving UK Prime Minister in the 20th century.

Adrian Hume-Sayer, Director, Specialist, Private Collections says: "The market's response to the historic sales in 2015 - both the online sale and the traditional live auction - was remarkable, with the overall result for The Mrs Thatcher Collection Part I and II far exceeding pre-sale expectations.

"Clients from all over the world seized the opportunity to acquire items which gave insights into the life of Britain's first female Prime Minister, who was a political giant on the world stage.

"In May, Christie's third and final sale in this trilogy of auctions coincides with the 40th anniversary of Mrs Thatcher's historic election, offering collectors, admirers and enthusiasts with one last chance to bid for a memento of 'The Iron Lady'."

Born on October 13, 1925 in Grantham, Mrs Thatcher was the daughter of local grocer Alfred Roberts who was also a local politician and twice became the Mayor of Grantham. She went first to Huntingtower Primary School and then Kesteven & Grantham Girls' School.

The Christie's sale is available to view online by clicking the red button below.

Photos: Christie's