NHS Test and Trace - seen as key to easing the restrictions - will be rolled out across England today with the help of 25,000 contact tracers, while an accompanying app is still delayed by several weeks.

Prime Minister Boris Johnson announced the launch of the contact tracing programme on Wednesday, which will see people with coronavirus having their contacts traced in a bid to cut off routes of transmission for the virus and control local flare-ups.

Under the plans, anyone with coronavirus symptoms will immediately self-isolate and book a test, preferably at a testing centre or, if necessary, for delivery to their home. Their household should start a 14-day isolation period too.

If the test proves negative, everyone comes out of isolation.

But if the test is positive, NHS contact tracers or local public health teams will call, email or send a text asking them to share details of the people they have been in close contact with and places they have visited.

The team then emails or texts those close contacts, telling them they must stay home for 14 days even if they have no symptoms, to avoid unknowingly spreading the virus.

Amid reports by Sky News that some contact tracers do not have their basic systems up and running yet, the Department of Health insisted that the "vast majority of our 25,000 staff have completed their training".