Disputing a red light ticket?

[Dodders]

My partner thinks he was wrongly accused of jumping a red light because it was still on amber. It was a police man that pulled him. Their were no witnesses and no photo evidence. He was at a T junction and slowed right down to turn right. But it was because of queing traffic that he was still in the road in the way of other traffic which made it look like he'd ran the red light. Would he have a good case if he disputed it? And how would he dispute it? Thanks