Boris Johnson is to write to every household in the UK urging people to remain at home "at this moment of national emergency" and warning that tougher lockdown measures may be needed to stop the spread of coronavirus.
In his letter to the nation, the prime minister urges the public to obey social distancing restrictions to prevent the NHS from being overwhelmed by patients.
Mr Johnson, who began self-isolating in Downing Street on Friday after testing positive for Covid-19, warns that “things will get worse before they get better”
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The publicity campaign, which will be delivered to 30 million homes across the UK, is estimated to have cost £5.8m.
“From the start, we have sought to put in the right measures at the right time,” the prime minister writes. “We will not hesitate to go further if that is what the scientific and medical advice tells us we must do
“It’s important for me to level with you – we know things will get worse before they get better.
“But we are making the right preparations, and the more we all follow the rules, the fewer lives will be lost and the sooner life can return to normal.
“It has been truly inspirational to see our doctors, nurses and other carers rise magnificently to the needs of the hour.
“Thousands of retired doctors and nurses are returning to the NHS – and hundreds of thousands of citizens are volunteering to help the most vulnerable.
“That is why, at this moment of national emergency, I urge you, please, to stay at home, protect the NHS and save lives.”
Mr Johnson adds that the lockdown, while disruptive to daily life, is “absolutely necessary” to save as many lives as possible.
“I know many of you will be deeply worried about the financial impact on you and your family,” he writes. “The government will do whatever it takes to help you make ends meet and put food on the table.”
The letter will be accompanied by a leaflet attempting to reduce confusion about the rules on leaving the house. Guidance will also be given about the symptoms of the virus, the shielding of the vulnerable and the merits of hand washing.