A contact tracing app could prevent one coronavirus infection for every one to two users who download it and it could be ready in weeks, according to an expert advising the Government.
Professor Christophe Fraser, from Oxford University's Big Data Institute, said the traditional way of contact tracing is not quick enough because of how rapidly the virus is passed on.
Academics from the university are advising NHSX, the health service's digital innovation unit developing the app, which would alert users if they had come into contact with someone who had tested positive for Covid-19.
Prof Fraser told BBC One's The Andrew Marr Show that around 60% of the population would need to download the app – which is aiming for a release "within