English: Coat of arms of Margaret Thatcher, The Baroness Thatcher (1925-2013), Prime Minister of the United Kingdom from 1979 to 1990. This achievement was used from 1992 to 1995, granted originally by the College of Arms in 1992 and was designed by the Garter King of Arms Sir Colin Cole. When she was appointed to the Order of the Garter in 1995 she was allowed to displayed a circlet of the order, she then used this new version until her death in 2013.

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On a lozenge circumscribed by the Ribbon of the Order of Merit with Cross pendant therefrom, surmounted by a baron's coronet, per chevron azure and gules, a double key in chief between two lions combatant a tower with portcullis in base all or, with supporters: dexter: An admiral of the fleet of the British Royal Navy; sinister: Sir Isaac Newton holding in his left hand weighing scales, both proper. Her motto was: "CHERISH FREEDOM"

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The dexter supporter is an Admiral of the Royal Navy, to commemorate the victory of the Falklands War during her premiership. The sinister supporter is Sir Isaac Newton, to recognise her earlier career as a scientist. The key and the two royal lions of England represents her tenure as Prime Minister and First Lord of the Treasury. The tower and portcullis represents her time at the Palace of Westminster as Member of Parliament. She bears this achievement on a lozenge (as is traditional for a woman), below hangs the ribbon and insignia of the Order of Merit (in which she was appointed in 1990).