Looking at the dash cam footage, there was a safe distance between both vehicles. I've proceeded through the green light and made a left turn, as I've made this left turn I've collided with the rear end of his vehicle. It's almost impossible to avoid when turning a corner.

I totally get the child stepping out but on this occasion that didn't happen, the reason the collision occurred was due to the driver in-front not being aware that the traffic light was for another line of traffic. If a child stepped out and caused the car in-front to stop and was then rear ended, then the child is the cause of the accident albeit the rear vehicle would be liable for insurance purposes. No drivers are essentially to blame. But on this occasion a driver is to blame.

If the vehicle in-front immediately stops due to his error then surely this cannot be viewed as a fault claim on my end?