More areas of England are to be subject to stricter coronavirus measures due to a rise in cases.
Here is a look at the three-tier system and what it means.
– Which areas are being added to Tier 3?
Health Secretary Matt Hancock told MPs in Parliament that Greater London, the south and west of Essex – which includes Basildon, Brentwood, Harlow, Epping Forest, Castle Point, Rochford, Maldon, Braintree and Chelmsford, along with Thurrock and Southend-On-Sea borough councils – and the south of Hertfordshire, including Broxbourne, Hertsmere, Watford and the Three Rivers local authority, will move into the highest tier.
The new measures will take effect on Wednesday.
– How does that leave the overall picture for the country?
Before the latest announcement 99% of the population in England was already living under Tiers 2 and 3.
Only the Isle of Wight, Cornwall and the Isles of Scilly are under the lightest Tier 1 controls.
London joins large swathes of the Midlands, Yorkshire, the North East and the North West in the most restrictive Tier 3.
– What is allowed under each tier?
Under Tier 1, people can meet a maximum of six friends or family outdoors or indoors.
Pubs and restaurants can open, but with table service only and an 11pm closing time.
In Tier 2, people from two different households cannot mix indoors, and outdoor gatherings are limited to six.
Pubs are to remain closed unless operating as restaurants, with alcohol only served as part of a “substantial meal”.
Retail and personal care – such as hairdressers and beauty salons – can open in all tiers, and indoor entertainment venues – such as cinemas, theatres, bowling alleys and casinos – are allowed to open in Tiers 1 and 2, but not Tier 3.
In Tier 3 areas the hospitality sector must close except for takeaways, and groups of six can only meet in outdoor public spaces.
– What about travelling within and between tiers?
People in Tier 3 areas should avoid travelling to other parts of the UK, including for overnight stays, unless it is for work, education, health or care requirements.
Mr Hancock said people in Tier 3 “should avoid travelling outside their area and reduce the number of journeys they make wherever possible”.
Those in Tier 1 and 2 areas should not travel to Tier 3 zones, but can pass through them as part of a longer journey.
Asked if people could still go into London after Wednesday to do Christmas shopping, Mr Hancock said: “It is recommended that people should minimise travel unless it is necessary in a Tier 3 area and should minimise travel where it is necessary to a Tier 3 area.”
– How are the restrictions determined in each area?
Mr Hancock insisted it was necessary to move the latest areas from Tier 2 to 3 to prevent the NHS being overwhelmed, saying “swift and decisive action” was needed.
He said there had been “very sharp, exponential rises in the virus across London, Kent, parts of Essex and Hertfordshire” in the last week.
When deciding on the tiers, the Government looks at coronavirus cases across all age groups and specifically among the over-60s, who are considered most at risk.
Officials also consider whether infection rates are rising or falling in the area and the positivity rate – meaning the number of positive cases detected as a percentage of tests taken.
Pressure on the NHS is also taken into account, including current and projected occupancy.