“The NHS has done it,” one minister told BuzzFeed News. “This has been an appalling few weeks, but we appear to have got through it without the worst happening.”

No exact plan to relax the lockdown has been finalised, government sources told BuzzFeed News, because it was too early to take decisions without knowing if the transmission rate of the virus, “the R number”, was coming down to a manageable level, and whether proposals to test and trace potential cases were viable. If either of these did not go to plan, restrictions would have to be extended again or reintroduced at a later date, they warned.

There are also a range of different options for how the UK could lift the restrictions, affecting different industries and age groups in different ways, based on as yet unavailable data. One source said the permutations at this stage were so varied and dependent on nonexistent data that they could not give a definitive picture of what life will look like in the months ahead.

However, ministers and government scientists are working on a broader three-stage strategy to ease some restrictions over the next three months, multiple sources familiar with the plan told BuzzFeed News.

The first stage, in what one minister said was a “best-case scenario”, would begin with schools and some businesses reopening in early to mid-May in order to get the economy moving again. Chancellor Rishi Sunak is determined to allow nonessential retail shops to reopen as soon as possible, as well as warehouses for businesses such as Next, which closed its operations last month.

The Treasury also wants to let as much of the manufacturing and construction industries get back to work as possible while encouraging proper hygiene and social distancing in the workplace.

People would be allowed out of their homes for nonessential shopping in this scenario, but most social distancing measures would remain in place. Some ministers are lobbying Downing Street to partially relax some other of the harshest rules in this first stage, such as those stopping people from sitting in parks or taking more than one form of exercise a day.

Commuters could be encouraged to wear masks on public transport if an ongoing review of scientific advice finds them to be effective at preventing the spread of the disease.

There are concerns in government that this is another area Britain has been slower to get on top of than other countries. The Department of Health told BuzzFeed News that no procurement of masks for the general public was yet taking place, and that it was still focusing on buying masks for NHS and care workers.

The second stage would see more businesses reopening and further social distancing measures lifted, and ministers hope this can start to take place by the end of May or beginning of June. This would mean most people returning to work and small gatherings being permitted. Later in the summer, the government hopes to be able to open pubs and restaurants.

SAGE scientists are also looking at lifting restrictions by age, raising the prospect that people under a certain age threshold could be able to go back to their offices sooner, organise social gatherings, or go to the pub — but those above the limit cannot.

Ministers and aides believe the development of new treatments for COVID-19 and the repurposing of existing antiviral drugs could have an important role in allowing the UK to move to stage two. Aides have been optimistically sharing news in their WhatsApp groups this week that a drug called remdesivir has shown signs of alleviating symptoms in patients in the US. There is now increasing optimism in Whitehall that by summer antiviral drugs could be used in Britain to give coronavirus patients a better chance of recovery and reduce death rates.

The third stage is the long-term final “exit” from the coronavirus crisis, when it is defeated once and for all and life returns to normal for the whole nation.

Government scientists have told ministers that there are only two routes to fully beating the virus: developing a vaccine, or the controversial “herd immunity” approach whereby a majority of the population get the disease, recover and can return to normal life.

Neither is a realistic prospect any time soon, with a vaccine thought to be a year to 18 months away — although scientists at the University of Oxford claim they could produce one by September — and doubts about how long immunity lasts. Until one of those two outcomes is achieved, the elderly and vulnerable must continue to be “shielded” with as many of the social distancing measures remaining in place as possible, a minister told BuzzFeed News.

Government figures are concerned that the public has not fully grasped the prospect of an effective indefinite lockdown for those over 70 and vulnerable groups. “‘You can’t see granny for 18 months’ is going to be an extremely unpopular and difficult policy to enforce,” the minister said.