The Queen has led tributes to the UK's war dead at the annual Remembrance Sunday service in central London.
Thousands gathered at the Cenotaph memorial in Whitehall for a two-minute silence to honour those killed in World Wars One and Two and later conflicts.
The monarch, Prime Minister David Cameron and the other main political party leaders all laid wreaths.
Events have also taken place around the UK, including in Edinburgh, where First Minister Nicola Sturgeon laid a wreath.
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This year's service at the Cenotaph was shorter than in previous years, in an effort to reduce the amount of time war veterans are made to stand.
However, plans to make political leaders lay wreaths together in order to save time were dropped after some politicians argued they were being overlooked.
The Queen was joined by royals including the Duke of York, Prince William and Prince Harry at the wreath-laying ceremony.
Mr Cameron was the first politician to step forward, followed by Labour leader Jeremy Corbyn.
Previous prime ministers John Major, Gordon Brown and Tony Blair also paid their respects, along with religious ministers, military leaders and dignitaries from around the Commonwealth.
BBC royal correspondent Peter Hunt
In the crowd, a young girl dressed in red applauded.
By the Cenotaph, a veteran in a wheelchair wearing medals and with a blanket, saluted.
They were just two of the many participants who had gathered before a structure which was meant to have been temporary when it was first constructed in 1919.
The wood and plaster of the original has been replaced by this permanent Portland stone memorial.
It's where monarchs have come, each year, to lead the nation's tribute to those who paid the ultimate price for the UK's involvement in conflicts from World War One to Afghanistan.
The ceremony, which has changed little down the decades, was slightly shorter.
This was in recognition of the advancing ages of the Queen, Prince Philip and many of the veterans.
Together, they had an opportunity to reflect, to remember, and to be reminded of the fragility of human life.
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King Willem-Alexander of the Netherlands laid a wreath after he was invited by the Queen to mark the 70th anniversary of the liberation of his country following the end of the World War Two.
Veterans took part in a march-past and military bands played a series of pieces.
Later falling poppies will be projected onto the Big Ben from dusk for the second year.
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Cdr Duncan McClement, from the Royal Navy, told the BBC the country must not forget those personnel serving today in conflicts around the world.
"There are also families for which this is the first Remembrance Sunday, who have lost loved ones on active service, and it's important that they, like all the others before through the great wars and all conflicts since then, are always remembered and never forgotten."
Robert Gale, who served as a landing craft signalman in the Royal Navy in World War Two, said "everybody around him was being called up" but he could not see himself as a soldier.
He said: "We went to Normandy. We landed at Gold beach. I helped the soldiers off the boat and one got killed by the side of me and I thought 'it's dangerous here but I didn't move'.
"They say 'war to end all wars' but it never works.
"I look back and think will this world ever be peaceful? I hope so because it's a wonderful world and everyone could and should enjoy it."
In Scotland, landmarks and buildings have been lit up in red as part of the 2015 Scottish Poppy Appeal, and Ms Sturgeon was among those who laid a wreath at the Stone of Remembrance in Edinburgh
A national service was also held at the Welsh National War Memorial in Cardiff, while further commemorations took place in Northern Ireland.
Ian Adamson, the former Lord Mayor of Belfast, collapsed at the cenotaph in Belfast during the act of remembrance.
His condition is not known.
A former soldier who lost his legs during the war in Afghanistan, Sgt Rick Clement,walked in the public for the first time at a Remembrance event at Blackpool cenotaph.
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Meanwhile, in Liverpool, thousands of ceramic poppies have been draped down St George's Hall. The display uses poppies from last year's Tower of London event, which marked 100 years since the start of World War One and drew more than five million visitors.
The Festival of Remembrance began in 1927 and was originally intended to honour the sacrifices of those who died in World War One.
However, it now includes tributes to the war dead from all past and more recent conflicts.
This year marks a number of other significant anniversaries in the UK's military history, including the 75th anniversary of the Battle of Britain.
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