About 1000 people attended the service led by the Prince of Wales including the High Commissioners of Australia and New Zealand, and the First Sea Lord at the Australian War Memorial in London.
The head of the Australian Defence Staff in the United Kingdom, Brigadier Grant Mason, said the service was a moving one.
"No matter where in the world we are, it's important that we pause on April 25 and acknowledge the courage and sacrifice of our current and former service men and women.
"It's also important to remember all those others including our diplomats and allies who have served alongside us," Brigadier Mason said.
The Prince of Wales and the Australian and New Zealand High Commissioners laid wreaths.
The service concluded with the Prince signing the book of remembrance while the digeridoo played across Hyde Park Corner.
A wreath-laying ceremony was held later in the morning at the Cenotaph, attended by the Duke of Gloucester, and the UK's Foreign Minister, James Cleverly, and Defence Minister, Ben Wallace.
Leading Aircraftman (retd) Robin Atherton, who served in the Royal Australian Air Force in the 1960s, attended the Cenotaph service.
"It was lovely seeing so many people turn out and line Whitehall - it means so much to all of us", Leading Aircraftman Atherton said.
A thanksgiving service was later held at Westminster Abbey.
Anzac Day has been observed in London since King George V attended the first service at Westminster Abbey in 1916 to mark the anniversary of the landings at Gallipoli.
