The rapid spread of coronavirus has led to more lockdown measures being introduced.
A third national lockdown has taken effect, with all schools shutting to most students.
Already a total of 44 million people in England – 78% of the population – were living under the harshest Tier 4 restrictions.
But now people across the country are being told to stay at home other than for limited exceptions, with measures potentially lasting until March.
Boris Johnson ordered primary schools, secondaries and colleges to move to remote teaching for all students except for children of key workers or those who are vulnerable.
The clinically extremely vulnerable are advised to begin shielding again.
Lockdown regulations came into effect from 0001 on Wednesday, with MPs due to have a retrospective vote in Parliament later.
A legally-enforceable stay-at-home order applies across mainland Scotland and Skye, with people only permitted to leave their home for an “essential purpose”, such as essential shopping, exercise, caring for someone or being part of an extended household.
Anyone able to work from home must do so. However, those shielding to protect themselves from Covid-19 should not go into work – even if they cannot work from home.
Schools are closed to most pupils until February 1 at the earliest, meaning an additional two weeks of home learning for youngsters.
All of Wales is at alert Level 4, meaning people should stay at home, not mix with other households and not travel without a reasonable excuse.
Education minister Kirsty Williams announced on Monday that schools and colleges will remain closed until at least January 18 and move to online learning.
“Wales remains in the highest level of restrictions. Everyone must stay at home,” Ms Williams said.
– Northern Ireland
Northern Ireland is in the second week of a six-week lockdown in which non-essential retail is closed and people are urged to stay at home.
In beefed-up measures, stay-at-home advice is to become law from midnight on Thursday, with additional powers being given to the PSNI to enforce the measures.
Remote learning for most school pupils will be in place until the mid-term break in the middle of February.
First Minister Arlene Foster said discussions on exams including A-levels and GCSEs are ongoing and that a decision will be made on Thursday.
There is still little clarity on transfer tests for entry into grammar schools, which were initially cancelled only for the Association for Quality Education to announce they will hold a single exam in February.