London, April 7 -- British Prime Minister Boris Johnson was moved to an intensive care unit on Monday after his coronavirus symptoms worsened though his Downing Street office said he was still conscious.

Britain has no formal succession plan should the prime minister become incapacitated, but Johnson, 55, has asked Foreign Secretary Dominic Raab to deputize for him.

Johnson, 55, was admitted to hospital on Sunday night and had been undergoing tests after suffering persistent coronavirus symptoms, including a high temperature, for more than 10 days.

Downing Street had said he was in good spirits and still in charge, though his condition deteriorated in the early evening and he was transferred at about 1800 GMT to an intensive care unit ...