The Queen has been joined by Prince William for her first public engagement outside of a royal residence since March.
Her Majesty and the Duke of Cambridge visited the Defence Science and Technology Laboratory (DSTL) at Porton Down in Wiltshire.
The monarch ventured from HMS Bubble – the nickname for her reduced household of staff – for what was her first external engagement in seven months.
Along with her grandson, the two royals met scientists at the site near Sailisbury, including those who have worked in response to the coronavirus pandemic.
The DSTL at Porton Down carries out some of the most highly classified work to safeguard Britain's security interests, and is one of the UK's biggest capabilities for handling dangerous pathogens.
The Ministry of Defence and Home Office are among its customers, spending more than £600 million last year.
During the visit, the Queen unveiled a plaque, formally opening the new £30 million Energetics Analysis Centre, used by scientists for counter-terrorism work.
Gary Aitkenhead, Chief Executive at DSTL, said it was “fabulous” that Her Majesty and the Duke opened the agency's "explosive analysis centre".
“This building, and the four and-a-half thousand people that work across buildings like this at DSTL, use their world-class science and technology expertise to protect not only the military, but actually keep citizens in the UK safe,” he added.
The two royal visitors were also given a private tour of the Energetics Enclosure, where they were shown displays of weaponry and tactics used in counter intelligence.
They were also given a demonstration of a forensic explosives investigation and met staff working in counter-terrorism and security.
The Queen and William were also introduced to people involved in identifying the nerve agent relating to the Novichok incident in 2018 and scientists who are helping with the UK’s response to the COVID-19 pandemic.
The Queen and The Duke also met with military personnel who were directly involved in the response to the 2018 Novichok incident.
"[The Queen] was really interested, I think, in talking about the science that underpins some of the activities that we’ve been involved with throughout the Novichok and COVID response,” said Tim Atkins, Senior Technical Fellow CBDN Division, DSTL.
The Duke presented British Army Colonel Mike Duff, Assistant Commander South West and deputy joint commander for the decontamination of Salisbury, with the Firmin Sword of Peace in recognition of the military's work.