Gallipoli centenary marked by Queen and UK leaders
The Queen has attended UK ceremonies marking the centenary of the Gallipoli campaign in World War One.
She took part in a two-minute silence before laying a wreath at the Cenotaph in Whitehall.
The Queen was joined by the Duke of Edinburgh, Prince William and party leaders at the memorial parade.
She later joined a service of remembrance at Westminster Abbey, where she laid a wreath at the Grave of the Unknown Warrior.
A second day of services also took place in Australia, Turkey and New Zealand to mark the centenary.
The national flags of Australia, New Zealand, Turkey and the UK were carried through Westminster Abbey and placed close to the high altar as a sign of reconciliation between old enemies.
The eight-month campaign on the Gallipoli peninsula in Turkey was one of the bloodiest of the war and the first to involve troops from Australia and New Zealand.
The allied operation was an attempt to force the Ottoman empire out of the war.
The Very Reverend Dr John Hall, Dean of Westminster, told the congregation: "We honour today the courage of the men at Gallipoli.
"The memory of the Great War provides for us warning and encouragement. We are warned that war must involve terrible suffering and death. We are encouraged by the spirit of national pride and determination shown by those we remember this Anzac Day."
At dawn the Prince of Wales, together with Prince Harry, attended a ceremony at the Anzac commemorative site in Turkey.
At the Cenotaph, the Queen joined crowds paying tribute to the 131,000 troops who died during the Gallipoli campaign - including some 25,000 British military personnel and 10,000 from Australia and New Zealand.
Descendants of those who fought and representatives from countries involved in the operation attended the ceremony.
And the principal party leaders - breaking off from the general election campaign - were also in attendance.
In Scotland, First Minister Nicola Sturgeon and Scottish Secretary Alistair Carmichael joined veterans and members of the public to mark the anniversary at the Scottish National War Memorial at Edinburgh Castle.
Earlier, the Princess Royal took part in a dawn service at Hyde Park Corner, where crowds gathered to watch her laying a wreath at Wellington Arch.
And the Duke of Edinburgh joined a service of remembrance at St Paul's Cathedral in London.
At the scene: Daniel Boettcher, BBC News
Those gathered at the Cenotaph today heard music led by the massed bands - pieces drawn from some of the countries that took part in the Gallipoli campaign.
Those waiting along Whitehall listened in silence: service personnel, veterans of more recent conflicts, and members of military associations including the Gallipoli Association. Also present were descendants of those who fought in the campaign.
Among those watching was 10-year-old Edward Jackson, wearing the medals of his great-grandfather, Commander Arthur Mallet, who served in the Royal Navy and was injured during the conflict.
Near the Cenotaph, artist Nadir Imamoglu, who was born in Turkey but has lived in the UK for 40 years, has set up a sculpture based on a larger one he has created at the National Memorial Arboretum in Staffordshire.
It is made of young oak trees to reflect the ages of the men fighting at Gallipoli - the bare branches reaching into the sky. The sculptor explains this represents the arms of those injured in battle reaching out for help.
At dawn on 25 April 1915, thousands of allied troops launched an amphibious attack on the strategically-important Gallipoli peninsula, which was key to controlling the Dardanelles strait, a crucial route to the Black Sea and Russia.
Among other events held on Saturday at Gallipoli:
- Australia has been remembering its dead at a ceremony at the Lone Pine site
- Turkey is holding a service at the Turkish 57th Regimental Memorial
- New Zealanders are remembering their dead at the other upper level battleground of Chanuk Bair