Originally Posted by paddlers
I'm with Biffer on the chaining the trailer to the car. I'd far rather the thing used the back of mine to stop rather than anybody else !
If you have the load nose heavy as it's supposed to be it'll drag along the road & HOPEFULLY wedge itself under the rear without too much damage.
Here in the US (at least I think it's nationwide), we're required to use a pair of safety chains to secure the trailer to the tow vehicle (crossed under the tongue), plus (for braked trailers) a breakaway cable to actuate the brakes should the trailer still get loose.
Ideally, the chain length is adjusted such that if the coupler comes loose/fails, the tongue drops onto and is supported by the X formed by the chains, preventing the tongue from digging in and pitchpoling the trailer. In theory, it will be sloppy, but you will retain control of the trailer (and anecdotal evidence seems to point to this.)
Chains have to be slack enough to allow for turns, heavy enough to support the shock loads imposed on them, and taut enough to prevent the tongue from dropping onto the ground.