Most probably a Daurian Shrike on present evidence. This bird was the classic proof of never give up while the wind is still sort of OK; after several visits to Donna including the previous day with little reward we forwent a visit on the Sunday only to allow other visitors to stumble across this stunner. Very similar in plumage to the first Lincolnshire record also at Donna Nook in October 1978 and shown here https://www.grahamcatley.com/rare-birds-in-britain/lincolnshire-old-rare-birds-archive?itemId=e06nzbz4drkoqpbnth3dgn9f7uallx