Super Saturday Seabird Surprise

Mooching around Peacock's hoping for a Pintail when a Hobby shot over my head in hunting mode after some House Martins. It failed on this pass and drifted up over the wood to the south of the lake, by the "Village Pit", where it started spiralling upwards, presumably to gain height for another attempt. As I was watching it I noticed a fairly large bird drifting fairly lazily behind it and almost dismissed it as a Cormorant but then it jinked slightly and the wing shape made me reach for the camera. Going by the meta data from the 18 or so pictures I managed to fire off before it drifted off south out of sight the bird was on view for about 10 seconds and I would never have seen it but for the Hobby. How many other birds like this do we blissfully miss over our heads?