A trial of the English coronavirus app is getting under way.

It will be limited to residents in the Isle of Wight, the London Borough of Newham and NHS volunteer responders to begin with.

The app will be available in Apple and Google's online stores, but users will need to enter a code to activate it.

The software will tell users to self-isolate for a fortnight if the app detects they have been close to someone else diagnosed with the virus.

Baroness Dido Harding - who heads up the wider Test and Trace initiative - had earlier voiced concern about implementing the automated contact-tracing feature because of fears many people who had been falsely flagged might be told to go into quarantine.

The app has several other functions, including:

• An alert system that informs users of the coronavirus risk level close to their home, with the area defined by the first part of their postcode
• A QR barcode scanning facility, so users can check in when they visit a venue and be told if others there later tested positive
• A symptom-checking tool, which allows users to book a free test and get the results via the app
• A countdown function that comes into effect if they are told to self-isolate, so users can keep track of how long to stay at home

It initially works in five languages, with plans to add more soon.

The contact-tracing element of the software is based on Google and Apple's privacy-centric system.

The developers acknowledge there are still issues with the number of false positives. Handsets may incorrectly record that they were within 2m (6.6ft) of another phone running the app for 15 minutes or more when they were actually further apart. But the developers say they are still making efforts to reduce the error rate.

Part of the problem is that Apple and Google refuse to share the raw Bluetooth signal data involved. But the two firms will shortly release a new version of their tool that should improve matters.

More to follow