The prime minister, 55, said he was given ‘litres and litres of oxygen’ but ‘the bloody indicators kept going in the wrong direction’ and it soon hit home for him that there was no cure for Covid-19.

Getting emotional as he discussed his experience in an interview, the Tory leader added that it was ‘extraordinary’ that he recovered in time to be at the birth of his son Wilfred Lawrie Nicholas Johnson.

Speaking to The Sun on Sunday, the Conservative politician admitted he was reluctant to go into hospital, but doctors were ‘adamant’ and he was put on oxygen and fitted with a tube.

He said: ‘It was a tough old moment, I won’t deny it. They had a strategy to deal with a “death of Stalin”-type scenario.

‘I was not in particularly brilliant shape and I was aware there were contingency plans in place.

‘The doctors had all sorts of arrangements for what to do if things went badly wrong.’

Mr Johnson was forced to acknowledge how serious the situation was when he started to deteriorate and was admitted to intensive care on the Monday.

Although he never believed he would die, he said there was a ‘bad moment’ when ‘it was 50-50 whether they would put a tube down his windpipe.

He said: ‘That was when it got a bit . . . they were starting to think about how to handle it presentationally.’

The interview comes hours after the first picture of his newborn son was released.

Carrie Symonds posted a photo of her cradling their baby Wilfred to Instagram this afternoon.

The new mum also revealed that he was named after both parents’ grandparents, as well as the two doctors that saved the prime minister’s life from coronavirus in April.

She wrote on Instagram: ‘Introducing Wilfred Lawrie Nicolas Johnson born on 29.04.20 at 9am.

‘Wilfred after Boris’ grandfather. Lawrie after my grandfather. Nicholas after Dr Nick Price and Dr Nick Hart – the two doctors that saved Boris’ life last month.

‘Thank you so, so much to the incredible NHS maternity team at UCLH that looked after us so well. I couldn’t be happier. My heart is full.’

The two medics later shared their ‘warm congratulations’ with the couple in a statement that read: ‘We are honoured and humbled to have been recognised in this way, and we give our thanks to the incredible team of professionals who we work with at Guy’s at St Thomas’ and who ensure every patient receives the best care. We wish the new family every health and happiness.’

Dr Nicholas Price is a consultant in infectious diseases and general medicine, according to the Guys and St Thomas’ NHS trust website, with further expertise in infection prevention and control.

Professor Nicholas Hart is the director of the Lane Fox Respiratory Service at the Guys and St Thomas’ trust, and a professor of respiratory and critical care medicine at King’s College London.

He has expertise in rehabilitation and home mechanical ventilation with chronic respiratory failure, according to his profile.