First lunchtime visit to the Thames this year. I popped over to the little park by the Houses of Parliament for half an hour - it was a bit too cold to stay any longer. While I was feeding a fair chunk of my sarnie to a Black-headed Gull, I noticed a Great Crested Grebe suddenly surface on the river below - this is the first one i've ever seen here on the river although they're quite regular in St James's Park. So that made up for the lack of a Med Gull which had been seen on this stretch of the Thames over the weekend. I'll have to try again when the tide is lower as there weren't many gulls today.
As an aside I also added Woodpigeon to my office window list today - 18 months after moving in! Just shows how bleak it can be for very common birds in really built up areas.