Fortunately some investigation turned up just a bit of harmless pollarding, but since that large mature tree was cut down at the riverside I've been edgy.
No exciting birds on the river today, we're back to just Black Headed gulls and Starlings for the moment, with the odd Common or LBB thrown in as sweetener, but on my way back to the underpass some unusual calling drew my eyes to a treetop. The calling bird turned out to be just a Blue Tit (never thought I'd be saying just a Blue Tit, how this patch has moved on since this time last year...), but as I was looking upwards I caught sight of an unusual silhouette high in the sky. Got the compacts out and lo and behold, there was some kind of raptor being mobbed by a Crow.
Now, excuses in advance. I'm not good on raptors and have precious little raptor experience to draw on, but this doesn't look particularly falco to me. Wide wings and short body, and big flat wingtips. Also, it's much further up than I'd expect to see a Kestrel and is soaring in a very Buzzard-like fashion. The video was taken by holding the phone up to the compacts, which are little 8x jobs, so that should give you some idea of just how high this was. It also explains the camera shake and the general poorness of the quality.
So. Since the bird is being mobbed by this Carrion Crow we know they're at roughly the same altitude and have a useful reference point for size. As far as I'm concerned we have 3 birds which might appear over central London, barring escapes from zoos and collections, that fit the size profile in the below:
Apologies for all the waffle, but I just have a sneaking suspicion I might be about to make a fool of myself AGAIN with a raptor on this patch (if not quite as dramatically as last time). Ladies and gentlemen, I bring you... THE VIDEO:
And this will be going on Birdforum without the lengthy exposition.