Veterans and world leaders have gathered in a small village in northern France to begin a day of D-Day commemorative events.
The 75th anniversary has brought together veterans from Allied nations on both sides of the English Channel to witness an inauguration ceremony for a new D-Day memorial.
The memorial, which overlooks Gold Beach, records the names of more than 20,000 British servicemen who died in the D-Day landings and Battle of Normandy.
It depicts three soldiers advancing across the beach.
Theresa May paid tribute to the bravery and sacrifice of the “greatest generation” of service personnel who served during the landings.
“If one day can be said to have determined the fate of generations to come, in France, in Britain, in Europe and in the world, that day was the 6 June 1944,” she said.
“More than 156,000 men landed on D-Day, of which 83,000 were from Britain and the Commonwealth.
“Over a quarter of a million more supported operations from air and sea, while the French Resistance carried out extraordinary acts of bravery from behind enemy lines.
“Many were terribly wounded, and many made the ultimate sacrifice that day, and in the fierce sacrifice that followed, as together our Allied nations sought to release Europe from the grip of fascism.”
The Prime Minister read the names of several British troops who were killed during the D-Day landings and the Battle of Normandy.
“These young men belonged to a very special generation, the greatest generation,” she said.
“A generation whose incomparable spirit shaped our postwar world.
“They didn’t boast. They didn’t fuss. They served.”
Dignitaries will later be invited to lay memorial wreaths and the last post will be played at the site where more than 4,000 war dead are buried.
Nearby, in the town of Arromanches, around 300 veterans have gathered to commemorate their fallen comrades.
Events began at 6.25am BST, with the tradition of a lone piper playing a lament on the remaining Mulberry artificial harbour in the town, named Port Winston.
These young men belonged to a very special generation, the greatest generationTheresa May
The lament signals the time at which the first British soldier stepped onto Gold Beach at the beginning of the D-Day landings.
It was played by Major Trevor Macey-Lillie, of 19th Regiment Royal Artillery (The Scottish Gunners).
He played Highland Laddie, a tune based on a poem by Robert Burns.
Speaking after his performance, Pipe Major Macey-Lillie said: “That was nerve wracking to do but I feel very proud and it was a privilege to do it.”
Mrs May was completing one of her last engagements as a Conservative Prime Minister.
After her speech this morning, she looked out across Gold Beach with French President Emmanuel Macron.
She was joined by defence minister Tobias Ellwood, head of the British Army Mark Carleton-Smith and Nick Carter, Chief of the Defence Staff.