Designed to be a key component of the test, track and trace programme to forge a way out of lockdown, the NHS Covid-19 app has been beset by problems from day one – despite repeated claims to the contrary. After a trial on the Isle of Wight at the start of May, the contact-tracing app was meant to be rolled out to the rest of England by the middle of the month. That soon slipped to some time in June. Then on Wednesday it emerged that we would have to wait until the winter. Now – after much behind-the-scenes scrambling, and head-scratching in Westminster – officials have decided to ditch the app entirely in its current form. How did this calamitous state of events unravel so spectacularly? Inspired by Singapore’s perceived early success in releasing TraceTogether, the first government-backed contact-tracing app, NHSX – a digital unit run jointly with the Department of Health and Social Care (DHSC) – set about developing its own version at the end of March. The following month, Apple and Google announced an unprecedented collaboration to leverage smartphone technology to help trace and contain the spread of coronavirus. But divisions between the UK’s approach and that of the two tech giants – denied at the time by NHSX – began to show later that month. A group of nearly 300 experts condemned the UK’s plans, citing privacy concerns over the centralised model. In the same week, France – one of the only other countries to pursue a centralised app model – publicly attacked Apple and Google for not loosening privacy protections. In early May, with a trial already under way on the Isle of Wight – where questions were raised about glitches on some phones and the potential lack of take-up among the island’s older population – it emerged that the government had left open the prospect of ditching the app in its current form. It was revealed that a feasibility study into moving to a “decentralised” model was under way. By mid-May, with the promised nationwide rollout nowhere to be seen, the Guardian reported that the app’s advisory board was split over whether it had the authority to tell the government to ditch its version and switch to a decentralised model. Members told of concerns that a lack of transparency and a rush to deploy the technology without proper testing risked compromising the project. As the days passed, ministers were accused of “misstep after misstep” when the Guardian revealed that applicants to become contact tracers were told recruitment was on hold while the government considered an alternative app. At the time, a DHCS spokesperson said: “The NHS contact-tracing app is not on hold and it would be completely wrong to suggest otherwise. There is no alternative app and the NHS continues to work constructively with many other organisations that are helping to develop and test the NHS Covid-19 app.” That statement has not aged well. Eventually, as cracks continued to emerge with the app, the “track” element of the government’s three-pronged approach was quietly dropped. Instead, the health secretary, Matt Hancock, unveiled the “test and trace” plan in England at the end of May. Now, in an embarrassing U-turn, it has been confirmed that it will switch to the model preferred by Apple and Google. At the crux of the matter has remained a key question: why did the UK government, unlike many others, continue to pursue a centralised model in the first place? The NHS app works by using Bluetooth technology on smartphones to register when people come into close contact with each other. Relying on users to flag up when they develop symptoms, it then uses a centralised database to alert others with whom they have come into contact that they are at risk of infection so they should isolate and get tested. Under the “centralised” model, information about who people came into contact with would be shared in an anonymised form with the health service, enabling tracking of both the data and the spread of Covid-19 but prompting privacy concerns. In the “decentralised” model, favoured by Apple and Google, no data is held in a single official database. Germany, Italy and Denmark are among other nations to have switched to a decentralised approach. Northern Ireland has already announced its intentions to develop a separate app to ensure compatibility with the one being developed by the Republic of Ireland, in order to aid cross-border travel. On Thursday, startling details emerged about the NHS app which help explain why it has finally been dropped in its current form. The app only recognised 4% of Apple phones and 75% of Android models. The alternative Google/Apple model can identify 99% of phones, but has problems distinguishing between whether somebody was 1 metre or 3 metres away. Given the problems, officials hope to find a “third way” by working with the two firms to create a tracing app that would work accurately. Officials refused to say how much money has been spent on developing the failed app, but an official database records three contracts worth £4.8m awarded to the company asked to develop the app, Pivotal VMWare. Without the help of the app’s technology, the government has relied on human contact tracers to get in touch with those falling ill and trace the peop0le they have come into contact with. The app has been recast as “the cherry on the cake” and deemed “not a priority”. However, early signs show that the human-only contact-tracing method is not working as smoothly as the government might hope – with figures showing approximately a quarter of people are not being reached. With no new launch date officially confirmed, many may be questioning whether precious time has been squandered. People will also be wondering how much longer they will have to wait until the app, which could prove crucial in tackling a potential second wave of coronavirus, is finally out.