Bird ID

[Renton Charman]

I was standing on the end of the pilotpier at Hartlepool Headland on Friday lunchtime when this bird came flying from the upper harbour out to sea. Thought at the time I had a guillimot in flight and only just looked at the photos and realised it wasn't. I've looked through Collins and the nearest match is a Long-tailed duck but may be way off the mark. Can anyone help? Photos in the poor light might have been better!

[TobyAW]

LTD it is

[Renton Charman]

Thanks Toby.