Queen Elizabeth on Thursday was carrying out her first major engagement since a coronavirus lockdown in March, visiting the Porton Down military research facility which was involved in dealing with a 2018 Novichok nerve agent attack.
The 94-year-old monarch, who spent Britain's national lockdown at Windsor Castle, has carried out her official duties remotely by video or telephone, or at her palace, since social restrictions were introduced. For her first public outing, she was joined by her grandson Prince William.
The top secret Defence Science and Technology Laboratory, in Porton Down in southwest England, identified the nerve agent used to attack Russian ex-spy Sergei Skripal and his daughter Yulia Skripal in the nearby town of Salisbury two years ago.
Britain has accused two Russian agents backed by Moscow of carrying out the attack, a charge the Kremlin has rejected.
During their trip, the royals were due to meet the Porton Down staff and other military personnel who were involved in the Novichok clear-up operation along with scientists helping the response to the COVID-19 pandemic.
The formal purpose of the trip was to open the lab's new Energetics Analysis Centre, where the queen and the prince will be given a demonstration of a forensics explosives investigation.
They were also due to tour the lab's Energetic Enclosure to see a display of weaponry and tactics used in counter intelligence.
Porton Down was founded in 1916 as Britain's chemical and biological weapons laboratory, where defense ministry scientists carried out secret experiments involving some 20,000 servicemen, leading to the death of one from exposure to sarin nerve gas.
Since the 1960s, it has focused on developing countermeasures and defense and security technology, although its secret structure has always led to speculation about its activities.
"No aliens, either alive or dead have ever been taken to Porton Down," the government's website says.
Since March, the monarch's only public appearances have been at Windsor for a military ceremony in June to mark her birthday, and for a ceremony to knight record-breaking charity fundraiser, 100-year-old Captain Tom Moore.
She has also paid private visits to Balmoral Castle in Scotland and Sandringham in eastern England, her private residences.