Patients in a coronavirus hotspot are reportedly being treated in ambulances as a surge in infections triggers massive queues for beds.
Images taken outside the Queen's Hospital in Romford, London, show medics in PPE interacting with patients and paramedics in ambulance parking bays.
One unnamed A&E doctor said the department was experiencing more cases and was "even more busy than the first wave", leading to a lack of beds.
They told Sky News: "The patients are first being treated by the ambulance staff as they are picked up from their homes. And then when they reach the emergency department they're waiting in the vans until a bed becomes available.
"Treatment is ongoing during that time and then they're waiting in the A&E department until a bed becomes available in the respiratory or intensive care unit. This can take a variable amount of time and is clinically determined."
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A paramedic at Medway Hospital in Kent said there was up to a six-hour wait for some patients arriving in an ambulance.
It comes as the number of coronavirus deaths in UK hospitals increased by 419 as senior doctors warned the NHS is "stretched to the limit".
Today, a further 365 deaths were recorded in England, seven more in Scotland, 14 more deaths were reported in Northern Ireland and Wales said there had been a further 33 fatalities.
Figures could appear larger due to a lag in reporting data over the bank holiday yesterday. It compares with the 488 coronavirus deaths recorded last Tuesday in the UK.
Some health boards are considering the option of setting up tents outside hospitals to triage patients, as they work in "major incident mode"
Emergency medicine consultant Simon Walsh, who is deputy chair of the British Medical Association's UK consultants committee, said such plans are normally reserved for dealing with major incidents such as terror attacks or big industrial disasters.
He said: "They are dealing with queues of ambulances outside many emergency departments, often with patients sat in the ambulances for many hours until they can be offloaded into the department because there simply isn't any space to put them in.
"Hospitals are even considering setting up tents that you would see outside in an actual major incident. All emergency departments have a plan for dealing with a sudden surge of patients from a major incident."
The flagship Nightingale Hospital in London has been stripped of equipment just at the time NHS bosses say they are about to be needed.
Beds and ventilators have reportedly been removed from the EXCEL centre after oxygen tanks were removed in November.
It comes as NHS Providers, which represents hospital trusts, said the “insurance policy” could be needed imminently but the NHS does not have enough staff for them.
NHS figures reveal there are now more patients being treated for coronavirus in hospital than during the first wave earlier this year
As of 8am on Monday, there were 20,426 patients being treated for the virus in hospital compared to 18,974 on April 12.
It comes as the UK also recorded its highest daily increase of cases since the pandemic began - with 41,385 cases
Dr Yvonne Doyle, medical director at Public Health England, said: "This very high level of infection is of growing concern at a time when our hospitals are at their most vulnerable, with new admissions rising in many regions."
The figures come amid warnings that hospitals in the South are facing a rise in pressure due to the increasing number of coronavirus patients.
Salisbury District Hospital is under "intense and significant" pressure as staff deal with numbers of Covid patients only seen at the height of the first wave in April.
The hospital urged only those enduring a "genuine emergency" to seek help at A&E.
Hospitals in Gloucestershire are "extremely busy" dealing with more than 200 Covid-19 patients for the first time during the pandemic.
Saffron Cordery, deputy chief executive of NHS Providers, said: "We know that the rate of Covid-19 admissions is rising and some trusts are reporting up to three times the number of Covid patients than at the peak of the first wave.
"This means hospitals and also ambulance services in Tier 4 areas and beyond are incredibly busy, compounded by increasing staff absences due to illness and the need to self-isolate."
Dr Nick Scriven, immediate past president of the Society for Acute Medicine, called the trend "extremely worrying" and said "systems will again be stretched to the limit".
"It is not 'just the case' of using the Nightingale hospital as there are simply no staff for them to run as they were originally intended (mini intensive care units)," he said.
"They could play a role perhaps if used as rehabilitation units for those recovering but, again, where do we find the specialist staff - the NHS simply does not have the capacity to spare anyone."
Paramedics in the capital are receiving support from other ambulance services in the South as they receive up to 8,000 999 calls each day.
London Ambulance Service described Boxing Day as one its "busiest ever days", with 7,918 callouts - up more than 2,500 on the 5,217 received on the same day last year.
Medics remained busier than usual on Sunday, with 7,111 calls, compared with 5,411 on December 27 2019.
The Mirror Online has approached Queen's Hospital in Romford for a comment.
