I'm pleased to report that the Kestrel has returned to its previous perch on the Tower of London. In fact today it was doing quite a bit of wandering over to the back of the bricked up window, where it was barely visible from the Tower path, before reappearing with feet overhanging the edge of the sill. This makes me suspect it may be looking for nesting sites, if it hasn't found one already. Not beyond the realms of belief as I have it on good authority that there used to be a breeding pair there, but it seems a strange location with the front being so exposed. On the other hand:
Kestrels do not construct nests of their own, but lay their eggs either in the old nests of crows, or in cavities in trees, or ledges on cliffs and buildings
If it nests in that window the views will be fantastic.
And as an aside, who needs real owls when you can have pictures like this: