Slaty -backed Gull on the tip

A couple of weeks ago I was asked to take part in the high tide count on Sunday 20th February along the Thames with other birders to count the waders in roost, my position was to count from the stone barges at Rainham Marshes. As I got out of the car a fellow birder said to me "thought there would of been more birders here" and I replied "erm I thought it was just me doing the count here?", the guy said "NO the Slaty-backed Gull back am I in the right place?". I replied "WHAT THE F..K" so it was a long run back to the tip and viewed the bird from the fence with the other 30 birders who were there. It did look like a right brute of a bird and the wide tertial crescent stood out really well, so, do I sound lucky?, well yes but I did miss it three times before...........