Thanks. I think I should clarify that the car had not stopped to reverse into a space as there was no space to reverse into. I think looking back he had gone past the car park lane he wanted to go down and had then pulled over so that he cuold reverse back to it. At the time I thought he had pulled over to let me go by.

You are right and I should have been more patient.

To be fair when i am in a car park i always reverse into a bay, and always position myself so even the most obtuse individual should be able to see what is happening, i also indicate the direction i am bout to take, however unless the person behind makes it clear they are waiting for me to complete the reverse i tend to cover the gap to prevent one of the many chancers who would nick the space as you back in.

Without being there and seeing how each driver behaved, aggressive pushy or messing about if any apply, then it's difficult to say who might be deemed at fault.

This sort of minor incident would at one time have been sorted out with a gentlemans agreement for one side to pay the damage* , in such circs the innocent party would do their best to mitigate losses and no insurance claim would be made, but those days are now confined to forgotten history, so accident management mobs will make money, accident repairers will make money, one side will ride around in a brand new high image credit hire car for several weeks and that £250 bumper repair will end up a £3500 bill for the deemed blameworthy's insurer and possibly more if whiplash pains suddenly manifest.

*SWMBO reversed into an older chaps car in a car park a few years ago, she told him she would pay for his damage, he contacted her with a reasonable estimate of i think around £150 might have been £250, he received a cheque for the amount the next day, the letter he wrote back in surprised thanks was really quite moving.