I grabbed my camera and took a few shots but then I realised it was more than just a tiff over territory. One bird was bleeding around the head and things looked serious so I thought I'd better break it up before the loser got even more injured. I walked up to them and at the last moment they flew off but within seconds the injured bird had attacked its oponent again and they were hard out fighting again.
I took more photos til I couldn't stand it anymore and broke it up again. Within half a minute they were locked in battle again. This went on for minutes til I chased them away across the road and they chased each other along the riverbank.