Or a MechLock? It's totally mechanical so no electrickery bits to go wrong, which is quite likely in a Land Rover which is driven through water/mud/crud regularly. It's an Italian invention and it's been around since 1989 and they claim not to have had a single claim(I'm getting all this shpiel out of LRW magazine...) It's basically a valve in the clutch system which locks the clutch open so the gearbox is isolated from teh engine. You just lock it on and off with a seperate key.
Is some scum-bag sees a steering lock, there's a chance they can get it off. If they see no steering wheel, they're pretty screwed and it's probably not worth the hastle!
The death penalty would be a nice deterant if I fancied going theiving!