Why can’t I just use a normal power board thats got a breaker installed?

You can buy power boards that provide overload protection. They are “for indoor use only” and they don’t have 15A outlets: they are illegal for use with caravans and RVs.

The RV02-MAX provides weather proofing to IP55, has a cleat which stops the lead being pulled out, and it has a hook that allows it to be hung up. The orange safety colour also warns people not to step on it or drive over it.