Just out of interest, I used the facility on the coronavirus section of the BBC website to see how many COVID-19 cases had been identified in my borough. There were 5. Westminster had 24; Surrey 15; Suffolk 1; and Norfolk 0. In the UK, there were 1,372 out of over 40,000 tested.
www.bbc.co.uk/news/uk-51768274
These numbers will undoubtedly rise but, even so, it might make it difficult to enforce tough national measures across the UK just now.
Perhaps someone will soon suggest sealing off the border between Westminster and surrounding boroughs! There is a certain irony that, within the EU, the response in a growing number of countries is to close their borders.