Dozens of sombre-faced locals queue outside the library in Pollards Hill, south London. They are waiting to receive a swab test which will hopefully tell them — and the government — whether they have been unwittingly infected by a new and concerning variant of Covid-19.

One of the most troubling to date, first identified in South Africa and known as 501. V2, has been found in more than 100 people in the UK, at least 11 of whom had not travelled to South Africa. As a result, ‘surge testing’ has been rolled out in over a dozen neighbourhoods across the country. Every single resident is being called upon to get tested, whether or not they have symptoms.

After months of missed targets and criticism, the spread of the variant poses the ultimate challenge for England’s test and trace system.

Decisions about how safe it is to loosen lockdown restrictions hinge in large part on the programme living up to its fundamental mission — to locate specific clusters of the virus and ensure they spread no further.

Adding to the urgency to find people infected with 501. V2, over the weekend a study emerged which found that the Oxford/AstraZeneca Covid-19 vaccine — the mainstay of the UK’s vaccination programme — does not appear to offer protection against mild and moderate disease caused by the variant.

Mario Lee, who lives in Pollards Hill ward, part of the London borough of Merton, said he is “seriously concerned” about its spread, in part because he feels as though the government had been “negligent as hell” in containing the pandemic so far.

“We never seemed to get on board with the fact that there were going to be variants,” he said. “We never developed a test and trace system that was efficient and actually worked.”

Lee was reflecting on months in which England’s testing and contact tracing programme was in disarray, with not enough tests, slow test turnround times and thousands of contact tracers idle for days.

Many of the teething problems have improved in recent weeks, and the programme is starting to look like a more credible tool in the government’s armoury for tackling Covid-19.

In a sign that lessons have been learnt, the programme’s leaders are now leaning heavily on local authority expertise and support to reach individuals in targeted locations where cases involving the new variant are known to have been found.

By Friday, Merton Council — where one case of 501. V2 has been identified — had already distributed 2,500 tests, and is aiming to reach 10,000 locals by the end of next week.

But as the programme sharpens to reach goals set for it by ministers and scientific advisers, gaps in the strategy have become more apparent: not enough people are coming forward for tests because they fear the repercussions of testing positive, which would require them to self isolate.

Mark Allison, leader of Merton council, wrote to prime minister Boris Johnson on Friday afternoon, asking that he scrap the means testing in place for payments to help support people who are self-isolating, and instead offer £500 to anyone found to have the virus.

“If it’s really this important, don’t miss out on the must vulnerable, the poor, the disadvantaged who are most likely to miss out on income,” the Labour councillor said. He added that several residents had confided that they were avoiding getting tested because they were scared of reneging on work or care responsibilities.

Baroness Harding, head of the NHS Test and Trace programme, admitted to MPs on Wednesday that around a fifth of daily contacts traced — roughly 20,000 people a day — are not self-isolating, according to government estimates.

“What’s missing from the equation is the people who have symptoms but who choose not to access a test,” said Adam Briggs, senior policy fellow at the Health Foundation, an independent charity and think-tank. “And at the other end of that piece is poor compliance with isolation.”

Candy and Teo, two volunteers going door to door to offer tests to Pollards Hill residents, said a small number of people had “aggressively” turned them away. “Some people don’t understand what’s going on or why we’re here,” Candy said.

The system has made strides in recent months. With testing capacity at above 700,000 per day, the UK has one of the highest rates per capita in Europe. More than 86 per cent of people who receive a positive result are being reached by the system as are 93.6 per cent of their named contacts — the highest since the programme was launched.

However, there are significant differences in the effectiveness of the system across local authorities. Since Test and Trace launched, 62 per cent of contacts have been reached by the programme in Bradford, compared to 89 per cent in Thurrock, according to the Health Foundation.

Test turnround times have also improved considerably, with 82.7 per cent of people who took tests at in-person test centres receiving their results within 24 hours, although the median test turnround time for home tests was closer to 35 hours.

One senior figure co-ordinating the contact tracing approach reflected on autumn last year when “we were coming in for a lot of stick”. Some of that he puts down to the “bonkers” system used for reaching out to several people in the same household.

He said the programme now runs on two tracks, depending on the scale of the pandemic. When the volume of cases is very high, the aim is to reach as many people as possible and notify them of risk using the contact tracing infrastructure in place.

When the volume is lower, the aim is a more ambitious type of “cluster busting” — identifying where the disease is spreading and engaging in sustained interactions with people there. This “cluster buster” approach is what is being used to root out cases of 501. V2, he added.

But to decide whether a positive Covid-19 case is infected with 501. V2, samples have to be sent off for genomic sequencing, which takes around eight days. So it may be some time before officials get a full picture of how far it has spread and how well the targeted and localised approach is working to contain it.

Lee at Pollards Hill took a test to play his part, but he is not convinced the strategy will work. “It’s a case of ‘the horse has already bolted, but let’s look as if we’ve done something about it’,” he said.