LONDON (AP) — Queen Elizabeth II on Thursday carried out her first public engagement outside of a royal residence since early March when the coronavirus pandemic started to impact upon on all aspects of day-to-day life in the U.K.

The 94-year-old monarch was joined by her grandson Prince William at the Defence Science and Technology Laboratory at Porton Down near Salisbury, in southern England, and met with scientists battling the virus.

The queen unveiled a plaque to officially open the new 30 million-pound ($39 million) Energetics Analysis Centre, used by scientists for counter-terrorist work.

Though the U.K. is in the midst of a resurgence of the virus, neither the queen nor William were seen donning a face covering but both observed social distancing rules of staying 2 meters (6.5 feet) apart from each other and anyone else. The queen had arrived by helicopter separately from the Duke of Cambridge, who had travelled by car.

A spokesman for the palace said all advice was followed.

All 48 people who were due to come into close contact with the royal pair had been tested for the coronavirus. All the tests came back negative.

Kensington Palace, the London residence of William, declined to comment as to whether the prince had also been required to have a test in order to be able to accompany his grandmother at Thursday's event.

The queen's last official public engagement outside of a royal residence was on March 9 when she joined the royal family for the Commonwealth Day service at Westminster Abbey. Before the U.K. was put into full lockdown on March 23, the queen and her husband, Prince Philip, had moved from Buckingham Palace to Windsor Castle, where they have been since.

Though living a far more solitary existence, the queen has been a visible presence over the past few months. She has been seen taking part in her first video conference call to support those caring for others, often in difficult circumstances at home during the pandemic. She has also addressed the nation on two occasions from Windsor Castle, in large part to bolster people's resolve in the face of the lockdown.

On signing the guest book at Porton Down, the queen quipped: “Well it proves we’ve been here, doesn’t it?”

It's certainly been a while since she could say that.