The key to reducing the lockdown is keeping a figure known as 'R' as low as possible.
R is the reproductive rate of the Covid-19 virus. For example, if If R is 1 it means that on average, each infected person is passing the virus on to one other person.
If R is above one then the virus is spreading exponentially. For example, if R is 2 then one person gives it to two people, who give it to a total of four people, who give it to a total of eight people.
However, if R is below one then the number of people with the virus will reduce.
In the UK, the Scientific Advisory Group for Emergencies (SAGE) assessed that R at the beginning of the epidemic was between 2.7 and 3.0. In other words, each person with the disease gave it to nearly three other people, on average.
But SAGE’s latest assessment is that, across the UK, R has reduced to between 0.5 and 0.9, meaning that the number of infected people is falling.
Note, however, that this does not mean the virus is any less infectious. It just means that the social distancing measures have given the virus less chance to spread.
So the Government's aim is to try to lift or at least to reduce some elements of the lockdown, while making sure R remains below 1.
If there does seem to be any danger that R will increase above 1 then lockdown measures will need to be re-introduced.
