"it was prone to 'pushing' on downhills. "

In Oz, trailers over a certain weight for cars (trucks had their own systems) used to have to have a mechanical brake (before the days of 'power braking), activated by cables going to both caravan wheels, and triggered by a setup that was activated by a sliding section in the hitch - braking caused the van to slide the thing forward, then hitting the brake trigger.

A real b****** if you wanted to back up and forgot to trip the manual 'safety' to allow that.... :-) ... and forgot to reset it after...