A major incident was declared across London today as the number of Covid cases and sick patients in hospital hit “critical” levels.

Mayor Sadiq Khan made the emergency declaration to fast-track national help for the NHS, which he said was “on the cusp of being overwhelmed” and running out of beds. The virus is “out of control” in the capital, he said, and Londoners are under orders to obey the lockdown and not mix over the weekend.

There are more than 7,000 Covid patients in London hospitals — almost 2,000 more than the first peak last April — and almost 1,000 are on ventilators.

Intensive care doctors said people aged 19 to 30 were being hospitalised with the new “Kent strain” of the virus and issued an alert to critical care colleagues across mainland Europe. A further 10,000 Londoners tested positive for Covid yesterday and the seven-day rate of 1,035.9 cases per 100,000 people is by some distance the highest in the country.

In another alarming development, infections are soaring in older Londoners, which will inevitably add to the death toll. By last night, 9,306 Londoners had died within 28 days of a positive test and 78,508 across the UK. In other key developments:

The number of cases in Londoners over 60 has quadrupled since early December, with many having caught the disease over Christmas.

Doctors warned that critical care nurses were close to burn out and were being stretched so thinly that there was a “very, very real risk” of patients suffering harm.

They said there was “no evidence” that high-pressure oxygen CPAP face masks offered better outcomes than invasive ventilation, with some patients deteriorating rapidly after long periods on CPAP.

New research indicated that the Pfizer vaccine may be effective against the Kent and South African variants.

The number of coronavirus “incidents” in care homes in the capital has risen, with 99 in the most recent week.

The Royal London, the capital’s biggest hospital, has more than 120 patients in intensive care and space for about 30 more. One doctor last night said he was unsure how they would cope if the number breached 150, amid fears that critical care will have to be rationed.

Professor Rupert Pearse told the European Society of Intensive Care Medicine that doctors had been “horrified” at the recent rise in cases in London.

He said: “The situation is genuinely serious. The workload is phenomenal. In my hospital we have more than 120 ICU patients. We are hoping that will stop at about 150 but we don’t know.