Prime Minister Boris Johnson has said he is sure US president Donald Trump will “come through it very well” as he is treated for Covid-19 in hospital.

Mr Trump announced his diagnosis in a tweet in the early hours of Friday, following a positive test from one of his closest aides.

Less than 24 hours later, the White House said the president would travel by helicopter to the Walter Reed National Military Medical Centre and would spend “a few days” there.

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Earlier, officials had said Mr Trump, 74, was experiencing “mild symptoms” of the virus which can notably cause fever, a cough and a loss of smell or taste.

Speaking to reporters on Saturday morning, Mr Johnson said he rang the White House on Friday night and added: “I think obviously everybody’s wishing him and Melania the very best and hoping that they recover speedily and I’ve no doubt that he will, he’ll make a very strong recovery.”

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When asked if he had any advice for Mr Trump, Mr Johnson said: “I think that he will be doing exactly what the doctors tell him to do and I’m sure he will be having the best care he can possibly get.”

He added: “I’m sure he’ll come through it very well.”