The coronavirus lockdown will have to remain in place for "several more weeks", one of the scientists advising the Government has said.

Professor Neil Ferguson of Imperial College said the social distancing measures appeared to be working better than expected but they would need to see more evidence the spread of the disease was being reduced.

"We made quite conservative assumptions about the level of contact reduction these measures would result in," he told the BBC Radio 4 Today programme.

"There is some preliminary evidence in terms of contact surveys, in terms of data from companies like Google about how people move, that we have seen even larger reductions in normal behaviour, contact, than we would have dared hope.

"That is good news but we have still got to see that reflected in case numbers coming down. It is only when we see the case numbers come down and how quickly transmissions have been reduced we can really conclude anything about what happens next, when these measures can be relaxed."

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Prof Ferguson said that the measures could be lifted in stages and he said there would need to be more testing for cases of the disease.

"Without doubt measures will be targeted, probably by age, by geography, and we will need to introduce - in my view - much larger levels of testing at a community level to really be able to isolate cases and more effectively identify where transmission has happened," he said.