A bird with hardly any sign of a pale trailing edge to secs.
And what about this one? It appears to have three different patterns in the secondaries. It is difficult to know for sure, but the different patterns may reflect different generation feathers. The white ones may be third generation, which suggests a moult rather different to Herring Gull. However, I don't want to overinterpret one image of one bird, so more work needs to be done on this issue.