I have discussed this with other birders, but this evening looked at the 'knees' of the two. The Seaforth bird had funny 'knobbly knees' - http://www.birdguides.com/iris/pictu...off=254242&v=0 (click on the + for larger images).
The Dutch bird had smooth 'knees' - http://www.dutchbirding.nl/images/fotos/fotoid2858.jpg
As well as other covert differences - notches in different places on the worn feathers. What do others think?