Families ripped apart by the tragedy were joined by senior politicians to remember those killed in the worst terrorist act over British soil.
The poignant wreath-laying ceremony was timed to coincide with the moment the bomb exploded on board Pan Am Flight 103, shortly after 7pm on December 21, 1988.
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Deputy First Minister Nicola Sturgeon and Scottish Secretary Alistair Carmichael joined victims' campaigner Dr Jim Swire, whose daughter died in the disaster, in London last night.
In the United States, a service of "hope and remembrance" took place at the Hendricks Chapel of Syracuse University in New York state, which lost 35 students who had been studying at its London campus. The service was followed by a procession to its Wall of Remembrance.
A scholarship scheme was set up between Lockerbie Academy and Syracuse University after the bombing. Claire Dorrance, a student who took part in the scheme in 2012-13, gave an address at the service. Her father, Sergeant Colin Dorrance, was one of the first police officers to arrive in the town the night of the bombing (see Lockerbie Voices, right). She said: "The 270 people who died are still such a force of good in this world."
A service also took place at the Arlington National Cemetery in Washington DC, which was attended by Scotland Office Minister David Mundell. He read out a message on behalf of the Prime Minister.
"For the fortitude and resilience you have shown. For your determination never to give up. You have shown that terrorist acts cannot crush the human spirit," he said. "That is why terrorism will never prevail."