Had been driving in the hills of the peak district in my 65 plate Auris hybrid.
Battery was the equivalent of two bars bellow a full charge, but was stuck in traffic with the ICE still running.
Tried to override into EV, but no joy for the best part of 10 minutes, with no strain being put on the drive train as it was all a steady downward stop start drive through some traffic lights.
Now, I know that at the end of a steep hill, with a very full Battery, the ICE will run for a shor