Carrie Symonds, the pregnant fiancée of Boris Johnson, has praised the medical staff, who helped the British Prime Minister come through COVID-19, adding that there were “very dark” times last week.

“I cannot thank our magnificent NHS enough.

“The staff at St Thomas’ Hospital have been incredible.

“I will never, ever be able to repay you and I will never stop thanking you,’’ she said on Twitter.

“There were times last week that were very dark indeed.

“My heart goes out to all those in similar situations, worried sick about their loved ones.’’

Johnson spent three nights in intensive care during his hospital stay.

Downing Street announced on Sunday he had been discharged and would continue his recovery at his official country residence.

The news came shortly before the governments of England, Scotland, Northern Ireland and Wales said that the number of coronavirus-related deaths in Britain had surpassed 10,000.

“In that past seven days, I have of course seen the pressure that the NHS is under,’’ Johnson said in a video message posted to his Twitter account shortly after he left St. Thomas’ Hospital in central London.

“I have seen the personal courage, not just of the doctors and nurses, but of everyone – the cleaners, the cooks, the health care workers of every description,’’ he said.

“The NHS is the beating heart of this country, it is unconquerable, it is powered by love.’’

The 55-year-old conservative politician was hospitalised a week ago running a high fever and spent three days in the intensive care unit.

In a statement late on Saturday, Johnson said of the health workers who took care of him: “I owe them my life’’.

Foreign Minister, Dominic Raab, is deputising for Johnson, but there are no clearly defined rules for situations in which a British head of government is not able to fulfil his or her duties.

Britain has recorded nearly 79,000 cases of COVID-19, the respiratory illness caused by the coronavirus.

Some 10,000 have died as the country’s National Health Service struggles to treat the large influx of patients. (Reuters/NAN)