"Given the early evidence we have on this new variant of the virus, and the potential risk it poses, it is with a heavy heart that I must tell you we cannot continue with Christmas as planned.
In England, those living in tier 4 areas should not mix with anyone outside their own household at Christmas, though support bubbles will remain in place for those at particular risk of loneliness or isolation.
Across the rest of the country, the Christmas rules allowing up to three households to meet will now be limited to Christmas Day only, rather than the five days as previously set out.
As before, there will be no relaxation on 31 December, so people must not break the rules at New Year.
I know how much emotion people invest in this time of year, and how important it is for grandparents to see their grandchildren, and for families to be together.
So I know how disappointing this will be, but we have said throughout this pandemic that we must and we will be guided by the science.
When the science changes, we must change our response.
When the virus changes its method of attack, we must change our method of defence."
(Boris Johnson, extract from Downing Street briefing yesterday)