I think just by focusing on individual boroughs or London as a whole misses the bigger picture of the spread of Covid in the south east.
I've been watching the south east figures for the past few weeks partly to inform the decision of whether to visit my mum for Xmas in south east London (or north west Kent as she prefers to call it). From what I've seen the roots of the current rise in figures go back before the last lockdown. Covid was taking off in north Kent and would've exploded disastrously if not for the lockdown, which held back the tide and saw falls in some of the worst affected areas (Swale, Thanet).
As lockdown 2 limped to its conclusion cases were already spreading along the north Kent coast - Medway, Gravesend, down to Maidstone. Since then cases have been steadily rising further south in Kent (the MP for Ashford was very outspoken against Kent going into Tier 3; cases there have risen 49.8% in the last week), into east London and along the south Essex coast. Most of the Thames estuary area has seen significant rises in the last week or two.
At first in London it seemed to be the north East that was seeing the biggest rise in cases. Even as London was declared Tier 2 case numbers were rising significantly in some areas such as Redbridge. Now cases are rising across most of the east - Bromley up 30% in the last week, Havering up 32.4% - and some central boroughs and western suburbs. Hackney up 33.3% in a week. Lambeth up 28.5%. Haringey up 54.3%. Some areas to the west are still doing okay - Hammersmith, Ealing, Brent, Hounslow are all down in the last week. But the spread has so far been continuing.
My mum is fine about us not visiting for Xmas this year.