The Queen today urged Britain to come together amid the coronavirus crisis and assured the country that the royal family was ready to "play its part" in beating the deadly infection.
The 93-year-old monarch was seen leaving Buckingham Palace with her faithful corgi-dachshund mix Candy on her lap as she headed to Windsor Castle for her Easter break a week earlier than planned.
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The Queen was joined at Windsor by her husband Prince Philip, 98, who travelled by helicopter from his home of Wood Farm at Sandringham in Norfolk, amid an anticipated lockdown of London.
She praised medical workers, scientists and the emergency and public services who are fighting the pandemic, and stressed everyone has a "vitally important part to play as individuals" - today and in the coming months.
"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," she said. "You can be assured that my family and I stand ready to play our part."
On another day of dramatic developments in the fight against the fast-spreading virus as latest figures revealed that a further 29 people who tested positive had died in England, taking the UK total to 137:
• Prime Minister Boris Johnson said the Government stood ready to take further action in London if people did not follow his advice on social distancing, although he ruled out closing down public transport.
Johnson also said UK scientists expect to start trials for the first vaccine within a month, as he thanked the public for the "huge efforts" they have taken in complying with the advice for the battle against the virus.
• The Bank of England cut interest rates to 0.1 per cent and unleashed another £200billion to boost the economy in its second emergency move in just over a week.
• The Department of Health and Social Care announced that £2.9b of emergency coronavirus funding would be made available to councils to free up at least 15,000 hospital beds.
• The Archbishop of Canterbury will lead a virtual service on Sunday, which will be broadcast on all BBC local radio stations.
• The Government's chief scientific adviser Sir Patrick Vallance said everyone must now follow the advice for social distancing, and socialising in pubs and clubs must stop.
Earlier today royal experts suggested Prince William could step in to cover the Queen's commitments in a crisis plan - due to second-in-line Prince Charles also being over 70 and potentially facing four months in self-isolation.
Her Majesty glanced out of the window as she sat in the back of her official car for the 50-minute journey to Berkshire.
Reports say the Duke of Edinburgh joined her a week early to match her revised schedule, as she waits out the crisis away from London, where tighter restrictions are expected within as it is the centre of the outbreak.
The Queen attended her last engagement in London yesterday, a private audience with two senior officers from the aircraft carrier HMS Queen Elizabeth.
Yesterday, she greeted Captain Angus Essenhigh, the new Commanding Officer of the Royal Navy warship HMS Queen Elizabeth, and his predecessor Commodore Steven Moorhouse.
There were no handshakes, just bows from the captain and the commodore, as they met and chatted with the monarch in the private audience room of the Queen's London home.
ITV's royal editor Chris Ship took to Twitter, explaining Philip had travelled by helicopter from Wood Farm in Sandringham to Windsor to be with the Queen for Easter.
"He had always planned to be with her and was moved to Windsor a week earlier to match the Queen's revised schedule," he wrote. "She arrived there this afternoon."
The Duke was last pictured in January being driven on to the Royal Sandringham Estate in Norfolk, where the Queen spends her winter break, for a shoot.
This week Health Secretary Matt Hancock said people over the age of 70 will be told to self-isolate, even if they do not have symptoms, in a bid to stem the spread of the disease and protect the most vulnerable in society.
Given Charles, 71, and the Queen, 93, are within this age group, as third-in-line to the throne the Duke of Cambridge may be required to provide a "physical presence" of the monarchy.
Nigel Cawthorne, author of Call Me Diana: Princess Diana on Herself told the Daily Mail's Femail: "It is entirely sensible for Prince William to act as placeholder for the Queen. There has to be a physical presence to the monarchy, not just a virtual one.
"He's third-in-line to the throne and in robust health like his brother, and Covid-19 is unlikely to be any serious threat for him or his wife or children. He will do a great job."
Royal commentator Robert Jobson also told Femail it is the "natural thing to happen" for the Duke of Cambridge to act as placeholder for his grandmother.
And Grant Harrold, who was a royal butler between 2004 and 2011, explained: "It is possible that if the Queen and the Prince of Wales are in isolation, then Prince William as second-in-line would take a more active role during this period."
Cawthorne added that, should the Duchess of Cambridge fall pregnant during the pandemic, the Palace would have to go "on bent knee to Prince Harry to ask him to act as placeholder".
"I am sure he would come back and be delighted to help out, too, and do anything to protect his father and grandmother," he said.
However, that could be difficult given Prince Harry is currently isolating in Canada with his wife Meghan Markle and their son Archie, who turns 1 in May.
Cawthorne acknowledged that it is unlikely there are any social gatherings left on the court calendar where William would need to step in, as the Queen has scaled back her events due to the outbreak of Covid-19.
However, he added, there are "classified informal meetings on matters of state, and the monarchy is an enormous machine with many employees staying in touch with people, cities and charities across Britain and the world".
"Some of these will be routed through secure communications. But this creates a risk of sorts and some of them will just require face-to-face meetings where Prince William can decide what is so essential that it needs to be managed up to the Queen or to his father.
"The organisation supporting the monarchy can't just stop. It would create an enormous backlog. Nor can a courtier stand in for the monarch and make all the decisions that are required to be made.
"Also, the Government will always want the head of state or a representative to be available when dealing with visiting foreign or diplomatic dignitaries. It always helps as the history of the British royal family is unparalleled."
It is also possible that Princess Beatrice, who is ninth-in-line to the throne, may be appointed a Counsellor of State during these uncertain times, while Harry - who is officially no longer a working royal from March 31 - may also step in to provide assistance, according to experts.
If the Queen is temporarily unable to perform her constitutional duties, normally there are five Counsellors of State available to fill in for her - Philip, 98, Charles, William, 37, Harry, 35, and Prince Andrew, 60.
Counsellors of State are made up of the consort of the Queen and the first four people in the line of succession who meet the qualifications - one of which is having reached the age of 21, which rules out Prince George, Princess Charlotte, Prince Louis and Archie Mountbatten-Windsor.