Meghan Markle appeared close to tears during a moving Anzac Day dawn service where fiance Prince Harry honoured New Zealand and Australia's war dead.
During the poignant event staged as the sun's rays broke over the London skyline, Ms Markle looked emotional as the hymn Abide With Me was sung by thousands gathered at the New Zealand war memorial.
The US actress, who wore a grey coat and large brimmed hat, passed a cultural milestone when she, and Harry, were given a traditional Maori welcome.
The couple were welcomed by Te Ataraiti Waretini from Ngati Ranana - the London Maori Club - with a traditional hongi, the soft pressing of noses and the sharing of each other's breath.
Ms Markle was making her first appearance at a service marking Anzac Day - April 25 - the anniversary of the start of the First World War Gallipoli landings, and a national day of remembrance for Australia and New Zealand.
Harry, a former Army officer who served for 10 years in the forces, led the nation's tribute to New Zealand and Australia's war dead by laying a wreath during the service at one of a group of metal crosses near Wellington Arch in central London.
A handwritten note from the prince, attached to a wreath of red roses, read: "For all those who have made the ultimate sacrifice in pursuit of our freedom. Thank you. Harry."
Kensington Palace said the Duke of Cambridge hoped to join Harry and Meghan at the afternoon Anzac Day service.
William, who is taking a few weeks off official royal duties now his son has been born, has yet to announce the name of the latest addition to his family.
Ms Markle may not yet be a member of the Royal Family but she has attended a large number of official events in the run-up to her Royal wedding on May 19.
There were other Maori cultural elements during the dawn service including a haka performed at the end, a longer version of the one displayed by the famous New Zealand rugby team the All Blacks before matches.
Ms Waretini said about Meghan: "She was amazing. I'm not sure if it's her first time at a Maori ceremony, but she did very very well.
"It was really lovely to meet her and share the breath of life and share our culture with her and Harry."
Trevor Mallard, speaker of the New Zealand House of Representatives, gave the address during the dawn service and said: "Today we remember 100 years have passed since the final year of the First World War. We honour the service of those who came half way around the world.
"Some with a deep conviction that they were fighting for king and empire, some fighting for peace and justice, others were young lads who saw an opportunity for adventure - none could have foreseen the hell on the frontline and in the trenches."
He added: "Today in thousands of communities throughout Australia and New Zealand people have come together to acknowledge and pay tribute to those who left our shores and particularly to commemorate those who gave their lives for our freedom."
Thousands of Anzac troops - Australian and New Zealand Army Corps - died in the ill-fated 1915 Gallipoli campaign.
Waves of Allied forces launched an amphibious attack on the strategically important Turkish peninsula, which was key to controlling the Dardanelles straits, the crucial route to the Black Sea and Russia.
But the plan backed by Winston Churchill, then first lord of the admiralty, was flawed and the campaign, which faced a heroic defence by the Turks, led to stalemate and withdrawal eight months later.
Its legacy is the celebration of the "Anzac spirit" - courage, endurance, initiative, discipline, and mateship - shown by the Antipodean troops and today the Anzac Day service in London has become an important moment for thousands of New Zealanders and Australians.
During the service prayers were read by young school children and the Last Post was sounded by a bugler before a minute's silence was observed by all.
After the service Harry, Meghan and dignitaries walked the short distance to the Australian war memorial where the prince laid another floral tribute.
Sir Jerry Mateparae, the high commissioner of New Zealand, who attended the service said later that Ms Markle was talked through the Maori elements of the service so she understood their significance and importance.
He added: "She was very interested, also it's her first Anzac service so we were explaining what it meant to us and the Australian memorial, so for her it was a new experience.
"The thing that was special in a way was the prayers led by the children and certainly Prince Harry and Ms Markle were impressed by the young people and the confidence of their delivery but also the way they conducted themselves."
Later, the Duke of Cambridge, Prince Harry and Meghan Markle attended a traditional Anzac Day service at Westminster Abbey.
The service was the culmination of a day of events honouring Australia and New Zealand's fallen, and those who have served in subsequent conflicts, which began with a dawn service and wreath laying.
The Very Reverend Dr John Hall, Dean of Westminster, told the congregation in the Abbey: "The landing of allied forces at Gallipoli on 25th April 1915 led to one of the bloodiest battles of the First World War.
"Australian and New Zealand forces joined together for the first time, and a new word entered the language: Anzac.
"Remembering that so many died, we honour the bravery and determination of the men at Gallipoli. The memory of what became known as The Great War is with us as a warning and an encouragement.
"We are warned that war involves suffering and death; we are encouraged by the spirit of national pride shown by the soldiers we remember this Anzac Day.
"As the Union Flag and the flags of Australia and New Zealand are presented at the High Altar with the flag of Turkey in a sign of the reconciliation of old enemies, let us renew our own commitment to the causes of justice and peace throughout the world."