London now has one of the lowest R rates in the country, according to official figures.

The closely-studied reproduction rate tells us how quickly the virus is spreading across the country.

The R rate - which refers to the number of people infected by each person with COVID-19 - needs to be below 1 in order for the number of cases to fall.

Figures published on Friday by the Government Office for Science and the Scientific Advisory Group for Emergencies (Sage) revealed the R rate for the UK as a whole is between 1.2 and 1.4.

And the R rate for London stands between 1.1 and 1.3.

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What is the R number?

The reproduction number is a way of rating coronavirus or any disease's ability to spread.

It's the number of people that one infected person will pass a virus on to, on average.

Measles has one of the highest numbers with an R number of 15 in populations without immunity.

That means, on average, one person will spread measles to 15 others.

Coronavirus (Covid-19) - known officially as Sars-CoV-2 - has a reproduction number of about three, but estimates vary.

How is R calculated?

You can't capture the moment people are infected. Instead, scientists work backwards.

Data - such as the number of people dying, admitted to hospital or testing positive for the virus - is used to estimate how easily the virus is spreading.

Why is a number above one dangerous?

If the reproduction number is higher than one, then the number of cases increases very fast - it snowballs like debt on an unpaid credit card.

But if the number is lower the disease will eventually stop spreading, as not enough new people are being infected to sustain the outbreak.

R ratings across the country

  • East of England - 1.2-1.4
  • London - 1.1-1.3
  • Midlands - 1.1-1.3
  • North East and Yorkshire - 1.1-1.3
  • North West - 1.1-1.3
  • South East - 1.2-1.5
  • South West - 1.3-1.6