Herring Gull or other gull?

[belbird]

I can never tell the difference between a Herring Gull and other gulls, eg common gull, greater or lesser black backed gull. Can someone tell me a) which ones you'd see on the Thames in the Chiswick area and b) which one this is? Thanks very much!

[Chocky]

They look like Lesser Black-back Gulls.
Herring gulls and Yellow legged Gulls are lighter Gery