The Princess Royal and Vice Admiral Sir Tim Laurence attended the Anzac Day Dawn Service at Wellington Arch, on behalf of The Royal Family.
Anzac Day – April 25 – marks the anniversary of the start of the First World War Gallipoli landings, and is a national day of remembrance for Australia and New Zealand.
Thousands of Anzac troops – Australian and New Zealand Army Corps – died in the ill-fated 1915 campaign.
A spokesperson for the Royal Family tweeted: "On Anzac Day we pay tribute to all those who gave their lives serving in the Australian and New Zealand Army Corps.
"Anzac Day marks the Australian and New Zealand landings at Gallipoli in 1915. This morning, The Princess Royal laid a wreath at both the Australian and New Zealand War Memorials, and signed a Book of Remembrance."
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.
Princess Anne and her husband were among a reduced number attending the Anzac Day Dawn Service at Wellington Arch, where the princess laid a wreath at both the Australian and New Zealand War Memorials, and signed a book of remembrance.
Later, the couple will attend the Anzac Day Service of Commemoration and Thanksgiving at Westminster Abbey.
Anzac Day has been commemorated in London since the first anniversary of the Anzac landings when King George V attended a service at Westminster Abbey.
Since then, the services have become an important moment for thousands of expatriates and visiting New Zealanders and Australians.
