Common Gull

According to my bird guide book this is a Common Gull in its second winter plumage, the speckled head and dark bar on the bill is the feature that indicates this.
 This was taken over our garden fence in the school playing field. We get a large flock at times, they gather and walk slowly across the grass in unison. I watched them recently with binoculars, and noticed that they stamp their feet rapidly as they move, I assume to disturb worms and insects.
 The things one does as old age creeps on!