Abstract
A Black Guillemot Cepphus grylle was present at Cut End on the River Witham in Lincolnshire on 7th–10th December 2017. Its strikingly white appearance suggested it belonged to the high-Arctic breeding form ‘Mandt’s Black Guillemot’ C. g. mandtii, previously unrecorded from Britain. The record was duly accepted by BBRC and BOURC as being the first British record of this taxon and added to Category A of the British List.Alan Harris