Red-footed falcon?

What was a fairly quiet evening back down at Marloes suddenly got a whole lot more interesting. I was just making my way towards Martins Haven and checking the field where the Hoodies had been when I spotted a presumed Peregrine heading in from direction of Skokholm, as it approached it appeared dark and smaller than I was expecting. It had now drawn level with me but still some distance and I could see no deep chest and it looked generally dark even allowing for the bright evening sky. As it continued in the direction of the mere I noticed the flappy wing beats and long wings. Not wanting to lose contact I followed it in the binocs across to towards mere where it suddenly veered off in a shallow dive and was lost to sight. Making my way back I had a good look around but no further sightings! Day off tomorrow I was going to try somewhere else for a change however...