The reproduction number, or R rate, of coronavirus transmission across the UK has dropped to between 1.0 and 1.2, according to the latest government figures.
R measures the number of people, on average, that each sick person will infect.
If R is greater than 1 the epidemic is generally seen to be growing; if R is less than 1 the epidemic is shrinking.
The estimate published on Friday is down from last week, when the Government Office for Science (GSO) and the Scientific Advisory Group for Emergencies (Sage) believed the R rate was in the range of 1.1 to 1.3.
Pushing the R rate below 1 is seen as vital to allowing any Covid-19 restrictions to be lifted, although it is just one measure on which Boris Johnson will base any decision.
The figures, for the entire UK, were released one week into the four-week national lockdown in England.
But there is a time lag on the data, and Sage cautioned it represents the situation over the “last few weeks” and does not reflect “any very recent changes” in transmission as a result of “recent policy changes”.
The GSO and Sage also publish regional R rates across England as supplied by NHS England.
Regional R numbers across England
East of England 1.1 to 1.4 (unchanged)
London 1.0 to 1.2 (down from 1.1 to 1.3)
Midlands 1.1 to 1.3 (unchanged)
North East and Yorkshire 1.0 to 1.2 (down from 1.1 to 1.2)
North West 0.9 to 1.1 (down from 1.0 to 1.1)
South East 1.2 to 1.4 (unchanged)
South West 1.2 to 1.4 (unchanged)
Nicola Sturgeon said on Thursday the R rate in Scotland “might be slightly below one”.
The latest data specifically from Wales, suggested the R number was estimated to be between 1 and 1.3.
Arlene Foster has said the most recent estimate in Northern Ireland is the R rate is about 0.7.
Sage said on Friday while there was “some evidence that the rate of growth in some parts of the country may be slowing, levels of disease are very high in these areas”.
“Significant levels of healthcare demand and mortality will persist until R is reduced to and remains well below one for an extended period of time,” the scientists said.
Johnson has all but promised the current blanket restrictions will end on December 2, after which England will return to some system of local tiered lockdowns.
MPs will get to vote on the next steps, and the prime minister may have to rely on Keir Starmer and Labour votes following the formation of a 50-strong group of Tory MPs opposed to any new lockdown.
Separate data from the Office for National Statistics (ONS) published on Friday suggested infection rates in England have increased in recent weeks, but the rate of increase is slower than previous weeks
According to the ONS study carried out between October 31 to November 6, around one in 85 people in England are infected with Covid-19.
More than 50,000 people in the UK have now died within a month of testing positive for coronavirus, with the grim milestone having been passed on Wednesday.
In March Stephen Powis, the medical director of NHS England, said a death toll lower than 20,000 would be “a good result”.
Datawrapper graphic provided by George Willoughby, MA data journalism student at Birmingham City University.