Grey back and rump
No interactions present.
As the identification has only been given to species level it is correct as the classification stands at the moment (White Wagtail, Motacilla alba, is the name given to the whole species - including the Pied Wagtail, Motacilla alba yarrellii).
IMO this IS a Pied Wagtail though (a bird at the end of it's first winter). The continental race,Motacilla alba alba, which is more frequently referred to as "White Wagtail", will tend to be a touch paler on the back and flanks,typically without the traces of darker plumage that seem to be present in this one (it's a very close call though).
I have seen plenty of Pied Wagtails about but they have always been much darker. I have never seen a White. I was unsure of this one as I figured it may just be younger Pied.
Lat/Lng: 53.556073179695, -2.1928440499306
OS grid ref: SD873066