Thank you, Ed and Pieter.
You are right about the framing. As so often happens, this was one of those times when nothing quite goes right. I got down to the river just about an hour before high water, to see what might be happening, got one nice shot and then spent the next half-hour looking for something else worthwhile. The light kept coming and going, as it does, but when the sun did get out it was glorious. As I was walking back to the car from the bridge, having pretty much given up, I visualised this scene. But to realise it, I had to climb over a three-foot wall, bash my way through a load of brambles and scrub, to get to the riverbank which turned out to be a sort of quaking bog with only one clear spot to stand on. You can imagine all this with yours truly and a Hasselblad with 50mm lens dangling round my neck, plus camera bag all snagging up in the undergrowth. At this point I found that the view to my right was completely obscured by flags and small trees, so this was the only possible frame. Then the fisherman kept getting up and moving around. When he sat down again, the sun went in. My right shoe was filling up with water. I lit several cigarettes in an attempt to pass the time. Eventually, he sat down, the sun relented and shone, and I got this picture.
It was a lovely evening, though.