A contact tracing app designed to help the UK emerge from the COVID-19 lockdown will be ready by the middle of May, it has been confirmed.
That is also the target time set to recruit 18,000 coronavirus contact tracers, although Matt Hancock, England's Secretary of State for Health and Social Care was unable to update further on how much progress had been made.
At Tuesday's daily Downing Street briefing Mr Hancock would only say "we hope to have the contact tracers in place before or at the same time as the app goes live".
With no obvious end in sight to the current policy of social distancing to contain the pandemic, and the prospect of a vaccine somewhere over the horizon, the Government's strategy for easing restrictions centres around a track and trace approach to fight COVID-19, save lives, rescue the economy, and restore some semblance of normality.
The policy was set out last week in a letter from Richard Gleave, deputy chief executive of Public Health England, to directors of public health who he said would be "essential in taking forward contact tracing for this next phase".
The broad approach revolves around an automated system to detect who has been infected with SARS-CoV-2, identify who they have been in close proximity to, and trace those individuals.
At the heart of the 'track' element of the equation is the CV19 app, developed by NHSX, the digital arm of the health service.
In common with the technology giants, CV19 uses Bluetooth low energy transmissions to log the distance between an individual's smartphone and other phones that have the app installed.
If a person becomes unwell, they can allow the app to inform the NHS which will assess symptoms for COVID-19 risk. If the disease is suspected, an alert will be relayed to other app users who had been in close contact with the individual over the previous few days.
The two models differ though in the approach they take.
Apple and Google take a decentralised approach in which tracking and alerting take place between phones. The system will reply on coded 'handshakes' between devices, and alerts triggered from a database.
From May, both companies will launch application programming interfaces (APIs) to underpin apps from public health authorities that will be interoperable between IOS and Android systems.
Privacy, transparency, and consent would be at the heart of their efforts, Google said in a blog earlier this month.
By contrast, the UK system would run via centralised servers, putting the NHS in control of who receives alerts.