Old breakaway cables were hooked through the bottom of the handbrake and crimped closed. Are the modern red alko cables supposed to be fitted the same way? I ask because the hook is about 10mm thick and solid.
You can close that sort up using a hand vice or a pair of large mole grips should do the job. You would be better getting an easy fit cable like this though.
Depends on the type of fitting you have on the brake end of the cable. If you have the fork and clevis type it fits directly to the hand brake assembly Link
If you have or can borrow a large pair of molegrips, hand vice or even a small clamp on bench vice that you can take off bench & use to squeeze it together then job done. Then otherwise I would take it back or just buy an easy fit type.
You could at least have taken a photo of yourself laying under the van with a bench vice, holding it up to the hand brake assemble trying to crimp the dam thing together.
------------- Just saying
If all is not lost where is it then?
The old style cables were not as thick and rigid but the newer type are unlikely to straighten out. The wife has already tested it by moving the car without unclipping it. I think if the handbrake wasn't on it would have towed the caravan away. The old one wasn't bad to remove but I think this one would need to be hacksawed off.