The 94-year-old monarch and her grandson Prince William visited the Defence Science and Technology Laboratory (Dstl) at Porton Down in southwest England, which has been helping to study Covid-19.

"It's doubling itself again," the queen remarked when discussing the current second wave. Being told it was on the rise, she said: "Well, I suppose it was expected?"

"Predicted ma'am, yes," replied Professor Tim Atkins, who coordinated Dstl's response, to which the monarch responded: "With all these horrible new things..."

The queen and William did not wear face masks but arrived separately and stayed two metres apart, while aides said all 48 people due to come into close contact with the royals had been tested for coronavirus.

It was the monarch's first public engagement outside one of her homes -- where she has had a reduced household staff known as "HMS Bubble" -- since she attended a Commonwealth Day service at Westminster Abbey on March 9.

As coronavirus swept across the UK, she and her husband Prince Philip, 99, retired first to Windsor Castle west of London, as a precaution because of their age.

They then spent time at her residences at Balmoral, northeast Scotland, and Sandringham, in eastern England, before returning to Windsor last week.

The queen made two televised addresses to the nation early on in the outbreak, which has killed more than 43,000 people in Britain -- the highest toll in Europe.

At Porton Down, the queen and Prince William also met staff involved in identifying Novichok as the nerve agent used to try to kill Russian double agent Sergei Skripal in the nearby town of Salisbury in 2018.

Skripal and his daughter Yulia survived the attack but a homeless woman who came into contact with a perfume bottle thought to have contained the nerve agent died four months later.

Britain and its allies blamed Russia and the incident prompted a mass expulsion of Russian diplomats by Western nations. Moscow denied any involvement.

During the visit the queen formally opened the new Energetics Analysis Centre, an explosive materials research centre.

She and William were due to be shown displays of weaponry and tactics used in counter intelligence.