Many thanks for these excellent additional photos.
They strengthen my view that this is not a Saker - the underwing looks pretty uniformly checkered with these additional shots and the jizz looks even less imposing. Saker is a real brute with a similar jizz to Pomarine Skua - muscular and heavy around the shoulders and neck - and with a sense of latent power. This bird almost looks slim enough to be an Amur Falcon in some shots.
I have been caught out before by brown juvenile Peregrine before at Mai Po a few years ago, and this reminds me of that that bird.
Cheers
Mike
