The new strain of the coronavirus could raise the R rate by more than twice as much as Boris Johnson has previously admitted.
Minutes from the Government's virus advisory group NERVTAG warn that the mutant strain could raise the UK's infection rate by as much as 0.93.
On Saturday the Prime Minister claimed that number was 0.4, before implementing a series of new restrictions in the South East.
R represents the average number of people each Covid-19 positive person goes on to infect. When the figure is above 1, an outbreak can grow exponentially.