A quick update on our visitor. I checked the photos we took with those in our bird book and it is definitely a rook. It has the distinctive white 'face' and pale beak whereas those of ravens and crows are black and much heavier looking. I phoned Secret World in Somerset this afternoon after checking that he was still in the garden! They are going to send one of their volunteers out to collect him as he shows no inclination to fly. He enjoyed some raw minced beef earlier and has plenty of other food and water at his disposal. I shall miss him when he goes but at the same time be relieved that he will be cared for properly.