As COVID-19 cases in London rise, people in the capital have been warned to follow the rules to avoid being moved into Tier 3.
Mayor Sadiq Khan said: “If we don’t all work together now, we may face tougher restrictions across the capital.”
London was placed in Tier 2 when England came out of its second national lockdown on 2 December, but the government will review each area’s allocation on 16 December, giving Londoners just a week to get numbers down.
Current infection rates are now above the national average and have been rising since mid-November, when England was in the middle of its second lockdown.
The number of infections in London’s older generation is slightly higher than England’s average, with 142 people aged over 60 reported as testing positive during the first week of December.
But there are large differences among London’s 32 boroughs.
Each 
represents a London borough, and at the end of November, the positivity rate was over 5% in all them. But there was up to eight points difference between the highest and the lowest.
Havering has the highest current infection rate in London – four times Richmond-upon-Thames, Westminster and Camden.
Barking and Dagenham, Waltham Forest and Redbridge join Havering in the top 20 local England authorities with the highest infection rates.
London 
Rest of England
They have among the highest infection rates in Tier 2, and have similar rates to many areas in Tier 3. Currently, there are 22 London boroughs over the average in England.
London Rest of England
The number of reported cases since mid-November –the middle of the lockdown- has also increased in 22 boroughs. Infection rates are decreasing in many areas placed in Tier 3.
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The infection rate in the over 60s is above the national average in 15 boroughs. But again, there are differences between boroughs. Havering has almost nine times the number of old people infected than Hammersmith and Fulham.
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Several different criteria are being used to determine which areas are in which tier: case rates in all age groups, case rates in the over 60s, the rate at which cases are rising or falling, positivity rate (percentage of tests which come back positive), and the pressure on the NHS.
The latest data shows the number of hospital admissions across London are considerably lower than the spring peak.
They are also similar to those recorded in other regions around England that have not been hit as hard as London by COVID-19.
The European Centre for Disease Prevention and Control said any increase of over 25% compared with the peak is a cause for concern.
With such a variety of rates across London, several Conservative MPs had called for boroughs to be looked at individually when assigning tiers.
But virologist Dr Stephen Griffin, associate professor at the University of Leeds’ school of medicine, said that would not help to reduce cases.
“In London, you’ve got public transport linking everywhere, you can walk around the corner and be in a different borough and people commute between many boroughs,” he said.
“The problem is none of the restrictions prevent people from moving around, so cases are always going to rise.
“We also don’t have track and trace working properly, so having the tiers split by borough would make it very difficult to trace infections.”