The Queen and senior royals joined servicemen and women past and present at the annual Festival of Remembrance as the nation remembered its war dead on Armistice Day.
A two-minute silence will take place at 11am where wreaths will be laid, followed by a veterans' march.
The Queen asked Prince Charles to lay her wreath at the Cenotaph instead of performing the symbolic duty herself. Britain's most injured soldier, LBdr Ben Parkinson, who lost both legs and suffered more than 40 injuries after a bomb blast in Afghanistan, laid a wreath in his hometown Doncaster.
The ceremony was led by Prince Charles, who laid a poppy wreath on behalf of the Queen, as she chose to stand by her husband the Duke of Edinburgh on the balcony. First Minister Nicola Sturgeon will attend the service.
The service was guarded by armed police and the Met confirmed it would be using facial recognition software to track crowds gathered to watch.
Also in attendance at The Cenotaph was Prince William, with pregnant wife Kate Middleton and The Queen.
Meanwhile, bell ringers are being sought for 2018 to honour the 1,400 ringers who died in World War One.
For Royal-watchers, the Cenotaph ceremony will have been a significant moment, as the heir to the throne represents his mother in one of the key public duties of the year.
A wreath will also be laid at the memorial for the Welsh Guards in London.
Charles has stepped in for the Queen at the ceremony twice before - in 1983 when she was in Kenya and in 1999 when the monarch had travelled to South Africa.
Millions of people fell silent as events were held across the country on Saturday to mark the 99th anniversary of the end of the First World War.
Among the acts performing were singers Mel C, Emeli Sande, Tom Odell, Lesley Garrett and Alfie Boe, alongside hymns, prayers, and readings.