Tony Cross sent the following having seen the photo which I posted yesterday:
Although I can only see the one leg there aren't that many likely candidates so
I reckon this bird is Black XO/BTO right leg;Blue/Green left. If so it was
ringed as one of a brood of two in one of our boxes near Aberystwyth on 16th May 2010.
It is a male and has previously been as far north as Cadair.