Prince Harry and Meghan Markle will join hundreds of Australians and New Zealanders to commemorate Anzac Day.
The couple will attend a dawn service in central London to remember the soldiers from the two countries who paid the ultimate sacrifice in the First World War and subsequent conflicts.
Later in the day, the prince and Ms Markle will join a Westminster Abbey congregation for a service of commemoration and thanksgiving.
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 on the Turkish peninsula.
The Dawn Service will be staged on Wednesday at Wellington Arch in central London and will begin at the New Zealand memorial where Harry will lay a wreath.
The prince, Ms Markle and Sir Jerry Mateparae and Alexander Downer, the high commissioners of New Zealand and Australian respectively, will then walk to the nearby Australian memorial, where Harry will lay another wreath and sign a book of remembrance.
Later in the morning at a wreath laying and parade service at the Cenotaph in Whitehall, Prince Harry will leave a floral tribute on behalf of the Queen.
Hundreds are expected to take part in the parade including members of veterans associations and ex-service personnel and their families.
At Westminster Abbey, Harry and Meghan will join the congregation for a traditional service where the Last Post will be played, an address made and Turkey's Ambassador to the UK will read the famous words of Kemal Ataturk - Turkey's founding father - from Anzac Cove.