To get to the spare, they needed to take all of their luggage out and pile it on the side of the road, which basically put up a reverse Bat-signal. Local criminals saw it and came running. A gang of six South Africans held the group at gunpoint and demanded money, weapons, and drugs. With little cash, less marijuana, and no deadly weapons (besides those chiseled cheekbones), Cumberbatch and friends were out of luck. They were thrown into a car and driven off. Cumberbatch complained that being tied up was interfering with his circulation (the most British response to a kidnapping ever), so the gang pulled over, took him out and began stuffing him in the trunk. That's when he had an idea.
He started ticking off numerous brain and heart problems he was suffering from -- including, apparently, a condition called "dying if I get locked inside a trunk." He told them, "I will die, possibly have a fit, and it will be a problem for you. I will be a dead Englishman in your car. Not good."
That Brit-corpse scent really sticks to the upholstery.
This, of course, was all a lie. Or, as it's called when beautiful people do it: acting. The kidnappers thought about it for a while and finally agreed. Cumberbatch and his friends were released. All because of the power of acting, and the fact that a dead Englishman is indeed terrible for the resale value of any vehicle.