Blackbird.........yes definitely a Blackbird. 100% white. It was amongst other blackbirds. I contacted the RSPB and was told Its snow white feathers are the result of leucism, a condition which affects the pigmentation of the skin. Unlike albinism, it does not turn the eyes pink. Birds with leucism or albinism have a shorter lifespan than others because they are more conspicuous to predators in the wild. A pure white one is very rare as even when they are first hatched they are thrown out of the nest at an early age. I am very privileged to have seen one.