LONDON (Reuters) - The United Kingdom put 20,000 military personnel on standby over the coronavirus crisis on Thursday as dozens of underground train stations closed across London and Queen Elizabeth left the city for Windsor Castle.

As the coronavirus outbreak sweeps across the world, governments, companies and investors are grappling with the biggest public health crisis since the 1918 influenza pandemic.

Against a background of panic buying in supermarkets and the biggest fall in sterling for decades, the 93-year-old queen issued a message to the nation as she relocated from central London to Windsor with her husband Prince Philip, who is 98.

“At times such as these, I am reminded that our nation’s history has been forged by people and communities coming together to work as one,” Elizabeth said.

“Many of us will need to find new ways of staying in touch with each other and making sure that loved ones are safe. I am certain we are up to that challenge. You can be assured that my family and I stand ready to play our part.”

In a sign of escalating fears about the impact of the crisis, the Bank of England cut interest rates to just 0.1%, its second emergency rate cut in just over a week, and promised an extra 200 billion pounds of bond purchases.

Prime Minister Boris Johnson said in a now-daily coronavirus news conference that Britain could turn the tide of the outbreak within the next 12 weeks.

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“At the moment the disease is proceeding in a way that does not seem yet to be responding to our interventions,” he said.

“I believe that a combination of the measures that we’re asking the public to take and better testing, scientific progress, will enable us to get on top of it within the next 12 weeks.”

However, he said he could not assert that the outbreak would be on a downward slope by the end of June. It was possible but not certain.

Britain has so far reported 144 deaths from coronavirus and 3,269 confirmed cases, but UK scientific advisers say more than 50,000 people might have already been infected.

LONDON LOCKDOWN?

Amid rumours that travel in and out of London would be restricted, Johnson’s spokesman told reporters there was “zero prospect” of restrictions being imposed.

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But asked about London later at his news conference, Johnson said compliance with the social distancing recommendations made by the government was patchy and it might be necessary to do more in the capital, although he did not specify what.

The government said police were still responsible for maintaining law and order and there were no plans to use the military for this purpose, though it did put military reservists on formal notification.

London’s transport authority said it would close up to 40 underground train stations until further notice and reduce other services including buses and trains.

“People should not be travelling, by any means, unless they really, really have to,” London Mayor Sadiq Khan said.

As panic buying continued and supermarket shelves were being stripped bare, an industry source said retailers were expecting police support. The government announced it was relaxing competition laws to allow cooperation between supermarkets to ensure supplies to the public were adequate.

Britain faces a “massive shortage” of ventilators that will be needed to treat critically ill patients suffering from coronavirus, after it failed to invest enough in intensive care equipment, a leading ventilator manufacturer said.

Johnson said Britain was in talks to buy a coronavirus antibody test that could be a game changer if it works, and that scientists were already making progress in finding medicines to fight the disease.

With the economy coming to a standstill, the pound on Wednesday plunged to its lowest since March 1985, barring a freak “flash crash” in October 2016. On Thursday the pound was down 0.5% at $1.1570.