Prince Harry and the Duke of Edinburgh have opened the Field of Remembrance at Westminster Abbey in London.
The royals spent nearly an hour meeting veterans and members of the Royal British Legion and Poppy Factory as they were led around the 100,000 crosses that have been planted in memory of fallen soldiers.
After arriving at the Abbey in a Rolls Royce, the pair paid their respects by each laying a small cross of remembrance in front of two wooden crosses from the Graves of Unknown British Soldiers from the First and Second World Wars.
David Cameron has welcomed military personnel, celebrities and singing group The Poppy Girls to Downing Street ahead of Remembrance Day.
The Prime Minister tweeted: "Wonderful to hear the Poppy Girls singing at No 10 to help support this year's Poppy Legion appeal."
The Duke and Duchess of Cambridge stunned hundreds of commuters in London today as they joined poppy sellers at a tube station.
The royal couple travelled on a Routemaster bus to High Street Kensington station where they met military personnel and volunteers supporting London Poppy Day.
William and Kate were swamped by members of the public taking pictures as they walked along the high street to the station's entrance hall.
Some 2,000 uniformed personnel, veterans and their supporters are hitting the capital's streets today for the Royal British Legion appeal ahead of Remembrance Sunday.
The Royal Navy's HMS Lancaster has paid its respect to the fallen by wearing a poppy ahead of Remembrance Day.
Thousands of miles away from the UK, the ship's staff gathered on the flight deck and created a bright red poppy before holding a moment of silence.
The ship is carrying out patrols in the Caribbean but remembered those who gave their lives, or have been injured, in duty.
The Duke and Duchess of Cambridge will welcome military supporters into their palace grounds today to mark London Poppy Day.
The royal couple will meet staff and volunteers taking part in the Royal British Legion appeal who will call at Kensington Palace as part of a tour across the capital on a 1960's Routemaster Bus.
Prince Harry and his grandfather, the Duke of Edinburgh, will pay their respects at the Field of Remembrance in Westminster Abbey.
Each will lay a Cross of Remembrance in front of two wooden crosses from the Graves of Unknown British Soldiers from the First and Second World Wars.
The Last Post will sound, marking the start of two minutes silence, after which the two royals will visit meet veterans of more recent battles.
The Duke and Duchess of Cambridge are also expected to attend separate Remembrance events later today.