Brabantia sp Image courtesy T. E. Scodirect
I left overjoyed, my morning hadn't been a complete waste. The 15 Black-tailed Godwit and single Little Egret on 'Bottom Tank' were almost superfluous. Now at last I had a record worth sending to the Durham county recorder. After a little research online I now think that this was probably a Brabantia 40L, if anyone else has noted this particular individual and can confirm the ID please leave a comment.