The PM has tweeted this ahead of today's UK briefing.
Boris Johnson
@BorisJohnson
·
4h
Everyone has a role to play in helping to control the virus by staying alert and following the rules. This is how we can continue to save lives as we start to recover from coronavirus.
#StayAlert
Prime minister to launch coronavirus alert system
An alert system to rank the threat level of coronavirus in England is set to be launched by Prime Minister Boris Johnson in his lockdown speech later.
The system, which will use a scale of one to five, is to be a part of the PM's televised address at 19:00 BST.
Mr Johnson will also explain any changes to the lockdown measures.
It comes after the "stay at home, protect the NHS, save lives" slogan was replaced with "stay alert, control the virus, save lives".
The "stay at home" advice will remain in place in
Scotland,
Wales and
Northern Ireland after leaders in the three devolved nations said Mr Johnson had not consulted them on the new message.
Scotland's First Minister Nicola Sturgeon said the only change being made to lockdown in Scotland was that people would be allowed to exercise more than once a day, from Monday.
The threat level system to be introduced will apply to England only but the government is working with the devolved administrations as they develop their own.
It is understood the system - with alerts ranging from green (level one) to red (level five) - will be adjusted according to data and will be similar to the one used to keep the public informed about the terror threat level.
In his address, Mr Johnson is expected to say England is currently at stage four but moving towards stage three.
More info at link and televised address at 19:00 BST.
Here is an additional link discussing the alert system and including the PM's tweet that I posted at the top.
Minister defends 'stay alert' advice amid backlash