The sacrifices of Australian and New Zealand forces will be remembered at a dawn service in central London marking Anzac Day.
A congregation will gather for the annual event commemorating the national day of remembrance for fallen Antipodean servicemen, former soldiers and those still serving.
The High Commissioners of New Zealand and Australia will attend the service at the Australian War Memorial at Hyde Park Corner along with fellow countrymen and women, with the Duke of York also due to pay his respects.
Wreaths will be laid at the Antipodean memorials and prayers said during the service.
Defence Secretary Sir Michael Fallon said: "On Anzac Day we remember the sacrifice and courage of troops from Australia and New Zealand. Britain is proud to have served alongside our Anzac allies in conflicts from the fields of Flanders to our modern day battle against Daesh.
"Our alliance is one of the most consistent and enduring military partnerships in history, one which will continue to protect our common interests and help make the world a safer, more secure place."
Anzac Day has been commemorated in the capital since the first anniversary of the First World War Anzac landings at Gallipoli in 1916, when King George V attended a service at Westminster Abbey.
Anzac Day will also be marked with a wreath-laying ceremony and parade at the Cenotaph, due to be attended by the Defence Secretary and other dignitaries.
Later, the Duke will join the congregation at Westminster Abbey for a Service of Commemoration and Thanksgiving.
Alexander Downer, Australia's High Commissioner to the UK, said: "Anzac Day is one of Australia's most significant national commemorations.
"We remember and give our thanks to those who have served and died defending our values and freedoms - truly embodying and immortalising the Anzac spirit."
Sir Jerry Mateparae, New Zealand's High Commissioner, said: "This Anzac Day we reflect on the enormity of loss we suffered 100 years ago. More New Zealanders died, in battle, in 1917 than in any year since."
