Why are spare wheels underslung on modern vehicles like my Discovery 4 and thus vulnerable to theft?

My 2012 Land Rover Discovery 4 went in for its first service and I was told that the spare wheel was missing. The service engineer at Lookers said they had seen a dozen similar cases where the cable is bolt cut through and the spare wheel dropped down and stolen. I called customer relations at Land Rover and the person said he had never heard of this. Very strange. If one garage has had 12 cases at least it must be a common issue and thus a design fault. Should Land Rover be obliged to make a security improvement? I am concerned that as soon as it is replaced at £1000 it will be stolen again.

Asked on 26 October 2013 by MT, London SW16

Answered by Honest John
I found the answer to this in Thailand, sold for pick-ups that have similar underslung spare wheels. It's a lockable through-bolt. I brought a sample back and was considering marketing them, but it involved too much risk for too little reward, so I took it no further. And no one else seems to have done so either. Same problem with Hyundai Santa Fes, KIA Sorentos, Range Rover Sports, all pick-ups and numerous 7-seat MPVs that come with an underslung spare.
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