What was the large flock of black and white bunting size birds on Exeter high street last night (13/022024)?

Link to video of Pied Wagtails in Exeter from 8 years ago to give some idea (unfortunately no close ups) ...
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A photo would help, but without one I'd still be almost certain that they were Pied Wagtails, which often gather to roos tin large flocks. Several years ago I watched a flock of more than 1000 Pied Wagtails roosting in the middle of Norwich. Passing shoppers identified them as all sorts of different birds, from Lapwings to Snow Buntings.
The black and white colouring is a very good clue, as is the fact there was a large flock. You'd be unlikely to find any flocks of buntings in the middle of a city, even Reed Buntings, and I think Snow Buntings would be extremely rare anywhere in Devon.