The Queen is marking the centenary of the Royal Australian Air Force (RAAF) during an open-air service honouring the Commonwealth country's airmen and women.
The event is her first public engagement outside Windsor Castle this year and is being held at the Commonwealth War Graves Commission (CWGC) Air Forces Memorial in Runnymede, Surrey.
More than 350,000 men and women have served in the RAAF since its formation in 1921, fighting in conflicts ranging from the Second World War to others in Korea, Vietnam and Afghanistan and Iraq, with more than 11,100 losing their lives in service.
The Duke of Cambridge is also marking the centenary with a video message that reflects on the service, courage and sacrifice made by generations of RAAF men and women.
Since the pandemic began, the Queen has carried out a handful of official events beyond the walls of Windsor Castle.
She was last seen outside her Berkshire home in November when she wore a face mask in public for the first time during a poignant visit to the grave of the Unknown Warrior at Westminster Abbey to mark the centenary of his burial.
The Queen has been carrying out her duties as head of state throughout the pandemic and has taken part in a number of virtual royal engagements via video call.
When the Queen arrived at Runnymede on Wednesday she was greeted by Claire Horton, director-general of the Commonwealth War Graves Commission, and George Brandis, high commissioner for Australia.