Rising numbers of coronavirus cases and the emergence of the new, more transmissible variant first identified in India have put the final stage of England’s lockdown easing in jeopardy.
Boris Johnson will announce on Monday whether Covid restrictions will be lifted.
As cases increase, Chancellor Rishi Sunak has said he is willing to accept a short delay to Step 4 of the roadmap to ending the lockdown, The Telegraph understands.
A Whitehall source pointed towards the Treasury having gone "long" on emergency coronavirus support packages in the Budget to cover the possibility of a delay to the plans.
Matt Hancock, the Health Secretary, said on June 6 the Government was "absolutely open" to delaying the final step in Boris Johnson’s reopening roadmap, which was the strongest indication yet that the so-called "freedom day" might be delayed.
Additionally, Jim McManus, the vice-president of the Association of Directors of Public Health, told BBC Radio 4’s Today programme on June 11 that the current restrictions should be kept going for four more weeks, and that if we "invest that little bit of time to keep us going forwards, it will stop us going backwards".
However, Downing Street said that data emerging over the coming days will be "crucial" in deciding whether all legal coronavirus restrictions can end as hoped.
Communities Secretary Robert Jenrick said on June 9 that coronavirus cases are "clearly rising" and that Mr Johnson is reviewing a range of data to make a decision on the further lifting of restrictions on June 21.
He told Sky News: "The Prime Minister is reviewing the data, and more data is coming in, which is very important.
"We created this five-week period between the stages of the roadmap and that has actually proved invaluable on this occasion, because it’s a finely balanced decision."
He added that the Government will look not just at whether cases are rising, but the link to hospitalisations and ultimately to death.
"So the Prime Minister is reviewing that ahead of the decision point, which is going to be June 14 – at that point of course he will let everybody know what the ultimate decision is," he added.
Here we look at what might happen if Step 4 of the roadmap is delayed.
What is due to happen on June 21?
According to the Government’s roadmap, Step 4 would see all legal limits on social contact removed.
It is hoped that the last indoor venues which remain closed, including nightclubs, will reopen and restrictions on large events and performances will cease to apply.
June 21 poll
Why might lockdown easing be delayed?
Mr Hancock said the emergence of the Indian (also known as Delta) variant, which is believed to be up to 40 per cent more transmissible than the Kent strain, had made the "calculation" on whether to proceed with unlocking "more difficult".
Scientists suggested that a steadily rising number of hospitalisations should delay the final stage of the roadmap.
The Prime Minister’s official spokesman said new data will help show "whether or not the excellent vaccine rollout programme has sufficiently severed that link between the increase in cases … and that subsequently leading to hospitalisations and deaths".
What could happen instead?
Mr Johnson is reportedly considering delaying the end of restrictions by at least two weeks in order to allow more people to be fully vaccinated.
A two-week delay until July 5 has been under discussion by scientists and civil servants, and after being queried about the delay, the Health Secretary reminded the public that the June 21 date was the earliest at which the government would take Step 4 – rather than being set in stone.
Mr Hancock also implied that some measures may remain in place after June 21. This could include further working from home, social distancing in bars and restaurants and mask wearing.
If the Government decides not to proceed with Step 4 of the roadmap, some indoor venues, such as nightclubs, would also not be allowed to reopen.
Limits on audiences in theatres, cinemas and sports events may also remain in place.
What are the scientists saying?
Professor Dame Anne Johnson, a member of Sage, said more data was needed to make a decision. She told Sky News that there had been a "significant uptick" in the number of cases in the past week or two, meaning that reopening as planned would be a "very finely judged decision".
However, NHS leaders have said that scientific modelling has been crude and unreliable at predicting the pandemic, and they warned against using it to decide whether to release restrictions on June 21.
Chris Hopson, the chief executive of NHS Providers, said trusts were "sceptical" about the fitness of models to provide useful forecasts for the pandemic.
How does this affect businesses?
UK business chiefs have warned MPs that a "generation" of firms could face collapse without further support, after piling up billions of pounds in debt during the pandemic.
Hospitality bosses have said that delaying freedom day would push many struggling businesses "closer to the cliff edge".
Kate Nicholls, chief executive of UK Hospitality, said: "The ongoing uncertainty around the roadmap is causing significant distress to hospitality businesses and operators.
"It is crucial that the Government commits to dropping the restrictions on June 21. Any delay in the roadmap would have a devastating effect on an already fragile sector."
Speaking to broadcaster LBC, Andy Haldane, the Bank of England’s chief economist, said that returning to normality is a “political decision”.
But he added: “It will be fantastic for the economy, another leg up, going up a further gear.
“It would mean that businesses could plan for a good summer and therefore would open up. It would mean that workers in those industries could plan for a good summer and socialise and spend.
"It would put the mojo back into both businesses and workers in a way that would I think lift our growth rates back up further above the levels we see across Europe and elsewhere.”
Government support for affected businesses remains in place until September.
What is currently allowed?
Most of the legal restrictions on meeting outdoors were dropped on May 17 after the Government pushed ahead with Step 3 of Mr Johnson’s roadmap.
People are allowed to meet indoors too, but the rule of six or two households still applies.
Indoor dining in restaurants is already permitted and customers are no longer required to purchase substantial meals with alcoholic drinks, nor to stick to a curfew.
Gyms have reopened and certain larger performances and sporting events in indoor venues have resumed.
Up to 30 people are able to attend weddings, receptions and wakes, as well as funerals.
When is the next lockdown announcement?
Mr Johnson has pencilled in June 21 for the final step in his roadmap out of legal restrictions, however, he will not make a firm decision about how to proceed until a week beforehand.
The Government has committed to announcing the plans on Monday, June 14.
What is permitted in the other UK nations?
In Wales, from June 7 groups of up to 30 people were allowed meet outdoors, including in private gardens, while up to three households can meet indoors.
The Welsh government is yet to give a date for the reopening of larger venues providing live performances or for events such as outdoor music festivals.
Plans to ease lockdown restrictions in much of Scotland have been paused, but restrictions were reduced in Glasgow, which had been kept in Level 3 restrictions due to a spike in cases.
Restaurants, cafes, bars and other hospitality venues in Northern Ireland can operate indoors, with six people allowed to sit together from unlimited households with table service only.