Most people do not tell their insurer about these sorts of things, the problem arises when there are opportunistic injury claims that follow afterwards and the insurance companies need to get involved months down the line.

In your case though, I assume your vehicle was empty, and the neighbour is totally at fault so there is no chance of this happening. Its up to you if you advise them or not, I cannot see that they would find out if you didnt given the circumstances.

I have to say, this is news to me! Are you honestly obliged to inform your insurer of an incident in which your vehicle was parked and empty, and the resulting damage from which was repared privately? An incident in which the insurance industry was in no way involved? This seems pointless, what does an insurer have to gain from this knowledge?

Keep quiet, they don't need to know anything about this. You are only giving them 'amunittion' with which to rip you off next time round.

It's a material matter that the insurer asks a very clear specific question about, ie "any accidents, claims or convictions".

Good insurers don't increase the premium after no-fault claims - but it's no surprise they don't trust any customers to tell the truth if the "keep quiet" attitude exists.

Yeah its a material fact! Insurers would just note it somewhere but its something that needs to be divulged.

If his car gets pranged repeatedly because his neighbour cannot drive for pennies, then the neighbour might not be so honest next time and keep quiet. Perhaps the next time it will be a random third party and its more to do with the area that this vehicle is parked. Just because this one time it was sorted amicably and off the books so to speak, it does not mean that the same will hold true next time.