The original NHS Covid-19 app, which was shelved, would have worked on a larger number of handsets than the app which launched in England and Wales this week, I have discovered.

VMware Pivotal, the firm behind it, has just published its software code.

It shows that it works on 97.5% of handsets, and provides more accurate measurements of contacts between users.

One expert told me the first app was better – but VMware Pivotal says it does not wish to compete.

The new app doesn’t work with a variety of older phones, including iPhones made before 2015, and Android phones not running the Android 6.0 operating system or above.

It can also generate false readings of close contacts in a third of cases.

“Compared to version two