Single paler bird present while there were several Pied not too far away. Photos enlarged - taken at the end of the camera range.
No interactions present.
These photographs don't convince me that this is a White Wagtail (M. a. alba) rather than a immature/female Pied Wagtail (M. a. yarelli) - although it could be the former.
Female/1st year Pied can be almost as pale backed as White Wagtails, and it looks like the paleness of the bird may be emphasized by slight over exposure in these photos (eg. in the first photo the black in the wings and tail also looks quite pale). One feature that does not look right for White Wagtail is the very dark appearance to the visible parts of the rump in the first photo, perhaps this is due to the rump being in shadow because of the wings?
The head and throat pattern would fit a winter male White Wagtail, or 1st winter/female Pied.
White Wagtails are certainly worth looking out for from now onwards, the first ones have been reported in Cornwall in the last few days, and more will be seen, particularly on the south and east coast, between mid March and late May.
This photo clearly shows grey flanks just under the wing - a feature of pied wagtail. See photos at the Portland Bird Observatory web site for Sept 2006
A lot of dark grey on the flanks is a feature of Pied Wagtail ( M. a. yarrellii), White Wagtails (M. a. alba) can have some pale grey on the flanks though - this is seen on some individuals within the normal breeding range of alba.
Examples can be seen in the photos from other European countries here (the ones taken in Britain/Guernsey could be argued to be yarrellii); http://www.birdguides.com/iris/pictures.asp?mode=search&sp=118063&rty=0&...
Identifying birds to subspecies level isn't always straight forward!
The paleness was very striking in the field, including the flank area. Although the photos are overexposed, the grey flanks do show quite clearly, so I would be happy to accept Pied.
Thanks for the links to other photos
Lat/Lng: 54.2, -5.9
OS grid ref: SB4686