What bird is this? We are puzzelled

Hello, Our Family Do Not Recognise This Bird...can you help...sorry pictures are not great. 

- bright white tail 

- tail fans out bright white when flying

- all brown body, slight light colour under chin

- no strips/spots etc 

- blackbird size 

Any ideas? We get all kinds birds, kites, swallows, robins, less and greater woodpeckers, owls the works but this one we are puzzled.