Dr Hilary Jones explained to viewers how the NHS' contact tracing app works, but also warned that there were some major problems with it.
Appearing on Good Morning Britain today with Susanna Reid and Piers Morgan today, Dr Hilary groaned when they were faced with pictures of packed beaches from yesterday.
Pointing out that it "made a mockery" of the app, he said: "If you test positive for covid-19 and contact tracer says, 'Where have you been in the last few days?' and you say, 'I was on the beach in Bournemouth or Southend-on-Sea amongst those crowds, who do you know who was next to you?
You can't possibly trace those people. And that's the problem. "When people start flouting the social distancing rules and we go out of lockdown in this