Hi Dave,
Best advice I can give is to go somewhere open and flat and try out your options. Use cones if you can get them - you'll look like a goose, but the cones don't mind being run over.
You can jack-knife a trailer to turn it sharply, but you still need a bit of room. IE, I'd driven into my backyard with a box trailer the other week, and needed to spend 5 minutes of back-and-forwards to spin the combo around. My backyard's not huge, but it's certainly wider than your hypothetical track. The longer drawbar of a camper trailer will make that trick both easier and harder. My point however is that by practicing how tightly you can turn your truck/camper combo, you'll at least have a baseline to go off if you do get into trouble. I learnt that even with a piddly box trailer, I need to cut the gardens back some more if I want to attempt that manouver again
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I agree with the gist of what the others are suggesting. If you can't reverse the entire thing, drop the trailer off, sort out the car, and come back for the trailer. In these instances a hand-winch and a few straps (plus knowning where you can attach them to the camper) can be worth their weight in gold - they let you secure the trailer in position, then winch it around slowly, etc. The only thing worse than being stuck on the side of a hill with the camper chained to a tree is being stuck on the side of a hill with the camper half way off the side, and a freshly-broken arm.
Worst case, as Jules says, secure the trailer and leave it. If you're that far in the poo, you need the car more than you need the camper
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Good luck!
Matto