ICU staff from Wolverhampton’s New Cross Hospital warned that “this time no-one is immune” to the virus. It comes as the UK registered 55,761 new COVID-19 cases on Friday.

Britain also reported a further 1,280 deaths related to the coronavirus in the latest 24-hour period.

On Wednesday the UK recorded its highest daily coronavirus death figure since the start of the pandemic, reaching 1,564.

Speaking to the Mirror, ICU nurse Suki Dhadda explained how the COVID-19 patients “are definitely getting younger”.

She added: “At the beginning of this pandemic they were at least in their 60s and 70s. Now they are in the 30s, 40s and 50s.

“We are seeing that no-one is immune this time around. People say ‘this is what you were trained for’, but we were never trained for a global pandemic.

“When you are treating patients in here with this virus who are in their 30s, not far from my age, we are not used to this.

“When they realise the severity of their situation they are shocked.”

On Friday, during a Downing Street press briefing, the prime minister announced a drastic tightening of the UK’s borders.

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Mr Johnson urged the public to stay at home in order to protect the NHS and save lives.

He added: “This is not the time for the slightest relaxation of our national resolve and our individual efforts.”

The prime minister’s warning came as a new strain of COVID-19 identified in Brazil has been detected in the UK.

Experts warned the strain may have been in the country for some time.

Professor Wendy Barclay, head of G2P-UK National Virology Consortium, a new project set up to study the effects of emerging coronavirus mutations, said one variant of COVID-19 found in Brazil has been traced in the UK.

Speaking at the launch of the new research group, Professor Barclay said: “There are two different types of Brazilian variants and one of them has been detected and one of them has not.

“In the databases, if you search the sequences, you will see that there is some evidence for variants from around the world, and I believe including the Brazilian one, which probably was introduced some time ago.

“And that will be being traced very carefully.”

In a separate statement, Professor Barclay said the Brazilian variant detected in the UK was not the one giving cause for concern.

She said: “The new Brazilian variant of concern, that was picked up in travellers going to Japan, has NOT been detected in the UK. Other variants that may have originated from Brazil have been previously found.”