Glaucous Gull By The River

At the weekend me and my partner had a walk by the river.  It was a bit chilly at this time of year but still very enjoyable.

We usually see lots of seagull on the river and also a strange looking type of gull (picture below).

On looking at the RSPB website, I believe it may be a Glaucous Gull.

A large pale gull with white wing tips. Younger birds are creamy white or more biscuit coloured, depending on age. All have pale wingtips. It is bigger than a herring gull and bulkier, with a fiercer expression, larger beak and squarer head than the smaller but virually identically-plumaged to the Iceland gull.

Any ideas?