Hello and welcome to more or less on the BBC World Service, the programme which sifts

through the haystack of numerical news looking for the needle of accuracy.

I'm Tim Haafard.

Last week, while schools and businesses across Europe closed in an attempt to halt the spread

of coronavirus, the UK stood alone in a more relaxed approach to the approaching pandemic,

letting people choose whether they wanted to go to work or socially distance themselves.

And this week, well, this week I'm speaking to you from under a duvet in my bedroom while

the schools prepare to close for the foreseeable future.

The British government says their change of heart was based on the work of scientists

like our guest.

My name is Crystal Donnelly.

I'm a professor at both Imperial College in the School of Public Health and also University

Voxford in the Department of Statistics.

So what has Crystal found that caused such concern?

She started back in January, analysing the number of cases of Covid-19 diagnosed in different

countries.

We were able to estimate what's called the basic reproduction number.

Now that's key to studying infectious diseases because that's the average number of people,

one infected person caused in a fully susceptible population.

Combining that information with how quickly those cases were being diagnosed can help explain

how the virus is spreading.

And so we estimated then a reproduction number of about two and a half, although that may

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