I think this is mostly just a feature of using the ONS data, which is random sampling of people but reports a week lagged.
If you look at the chart by Alastair Grant that you feature at the top of the UK section (with red and black dots), it looks something like a halving (or more) of Delta in the week from 13 Dec to 20 Dec.
That would also be compatible with the story of substantial behaviour change.
I think this is mostly just a feature of using the ONS data, which is random sampling of people but reports a week lagged.
If you look at the chart by Alastair Grant that you feature at the top of the UK section (with red and black dots), it looks something like a halving (or more) of Delta in the week from 13 Dec to 20 Dec.
That would also be compatible with the story of substantial behaviour change.