The app logs the distance between phones that have the app installed, using Bluetooth technology. If an app user develops symptoms of Covid-19, they can use it to inform the NHS, which will then send an anonymous alert to other users they have recently come into close contact with.

After the app has been tested in the Isle of Wight, it will be deployed more widely this month if the trial works, transport secretary Grant Shapps told the Andrew Marr Show yesterday ( 3rd May).

Use of the app is voluntary but the government will ask everyone in the UK to install it. 

It has been developed by NHSX, the technology arm of the NHS. NHSX is to take a ‘centralised’ approach, which sends data on who may potentially have the virus to a central computer server, in contrast to a ‘decentralised’ approach taken by Apple and Google in their new API.

Various groups have urged caution over the development of digital tools for tracking coronavirus infection, raising concerns over the potential for surveillance.

Last week, a group of over 100 UK academics working in information security and privacy shared their concerns about the NHS deploying a contact tracing app. “We urge that the health benefits of a digital solution be analysed in depth by specialists from all relevant academic disciplines, and sufficiently proven to be of value to justify the dangers involved,” the joint statement said.

A review from the Ada Lovelace Institute, published in April, found that there is currently no evidence to support the immediate use of digital contract tracing and symptom tracking, and said any such tools should be backed by ‘clear and primary legislation’ to regulate data processing.