It came as the Israeli doctor who caught the Omicron variant at a medical conference in London said the lack of masks on public transport may have caused the infection.

Dr Elad Maor, who is 45 and has received three doses of a Covid vaccine, told the Telegraph he was frustrated to see so many people going maskless on the London tube and DLR.

He said: “I am very frustrated and feel uncomfortable with people who do not wear masks and are reckless. You can see that many people were not wearing masks.I was using the tube and the DLR. Many people in the tubes were not wearing masks.

“I don’t know where I got it, but I feel like if all were wearing masks then the risk of getting it would be smaller.”

The cardiologist took extreme care to avoid catching or spreading Covid during his trip. He tested negative for Covid-19 prior to leaving Israel and also tested negative both before his return trip and upon landing in Israel.

He also wore a face mask, but said he wished he had used a more protective N-95 mask.

Dr Maor said he began to feel unwell on Friday, after returning to Israel, and spent 48 hours in bed with flu-like symptoms including fatigue, a cough and a sore throat. He added that he was still feeling “weak” and hoped to recover soon.

“I was questioned by the ministry of health in Israel once I was positive. They specifically asked me about the flight, what the seat was, and the flight number.  I don’t know if they contacted the ministry of health in London.”

The medical conference, PCR Online, was attended by around 1,000 people, mainly from European and Mediterranean countries.

Before he developed symptoms, Dr Maor said he had infected Dr Dan Elian, also a cardiologist at the same hospital.