Baroness Thatcher has joined Falkland Islanders and former servicemen to honour all those killed in wars in the South Atlantic.
Baroness Thatcher is regarded as a hero by many of the islanders
She laid a wreath at the Cenotaph in London's Whitehall to mark the annual Battle Day commemoration.
Lady Thatcher was prime minister at the time of the fight to retake the islands from Argentine occupation 25 years ago.
Veterans of the 1982 conflict also attended, including Lt Col Chris Keeble who freed the Goose Green settlement.
Col Keeble took over the leadership of 2 Para in the heat of battle after commanding officer Lt Col "H" Jones was killed leading a charge against an Argentine position, losing his life but winning the Victoria Cross.
A total of 255 British servicemen and three Falkland Islanders were killed in the conflict, sparked by the invasion on April 2, 1982.
They fought at sea and on land before Argentine commander General Menendez surrendered to the Britain's Major General Jeremy Moore on June 14.
The Reverend Peter Millam, a former Falklands padre, said a short prayer for the war dead during the service at which the Last Post was also played and a minute's silence observed.
"We must remember the fallen and the great sacrifice they have made," he said.
Security minister Admiral Sir Alan West also attended the ceremony. He commanded the frigate HMS Ardent which was sunk during the hostilities.
December 8 is a public holiday in the Falklands. Originally a commemoration of the naval Battle of the Falklands in 1914, those who died in all subsequent conflicts including the Falklands War are now remembered.
Lady Thatcher is patron of the Falkland Islands Association.
"She's the great hero of the islanders for sending the chaps down there to release them," said Colin Wright, the association's honorary secretary.