A counter argument may be that London is ahead of the rest of the country in acquiring immunity - and recent research suggests that rather than 60% of the population having been infected, it could take as few as 10% - 20% to provide herd immunity, provided the right people, i.e. those most liable to infect others, have been infected. London's economy could therefore bounce back far more quickly than the rest of the country, and dampen a drop in values. I don't understand why crowded, rammed, jostling London should be better off than the post-industrial NE, but there it is.
I've constructed the chart below from the Land Registry HPI for London, taking the flats values, and the ONS quarterly GDP data series, both rebased to 1995 = 100. Interesting. And that verse by Louis MacNeice from 1934 always comes back to me -
Splayed outwards through the suburbs houses, houses for rest
Seducingly rigged by the builder, half-timbered houses with lips pressed
So tightly and eyes staring at the traffic through bleary haws
And only a six-inch grip of the racing earth in their concrete claws;
In these houses men as in a dream pursue the Platonic Forms
With wireless and cairn terriers and gadgets approximating to the fickle norms
And endeavour to find God and score one over the neighbour
By climbing tentatively upward on jerry-built beauty and sweated labour.