Red-tailed Hawk Buteo jamaicensis
A common and widespread species in North America and a potential vagrant to the UK, but due to the number of escaped birds on the loose any vagrant is unlikely to be accepted as such. There have been a number of records of escaped birds at several sites in Norfolk in recent years.
There is significant geographic (as well as individual) variation in the plumage of Red-tailed Hawks in North America. All of the following photos were taken in the west, mostly in California, so they do not represent the full range of variation by any means.