I am sure this will not be approved by the local electricity board but I think it is perfectly safe
What happened: the charger to one of my booster battery packs got stuck between the car door and its jamb in a somewhat hurried packing action. Then I closed the door and realised it wouldn't. The plug integrated in the charger housing was shorn off.
Repairs involved a few lengths of heat shrink tube, some cabling, a mains plug, some solder, and four strategically placed zip ties which contrive to both hold the housing together and provide the requisite strain relief (as per code) on the cable
Works like a charm.