[SpyGuy]

I think the British might have been worried that if Hess had been killed while in their custody that Hitler would have responded by killing some British POW's.

That would certainly have been a valid reason. But the actual reason is irrelevant to my point: that some military prisoners have a tangible value that justifies the (relatively minuscule) cost of their incarceration, whereas common criminals (whose incarceration make up 99.9% of prison budgets) have no real value to society.

[Which, BTW, is why I have long advocated that the penal system should require inmates to work and pay for their incarceration costs, in addition to prosecution costs, law enforcement costs, and victim restitution.]

[mainepatsfan]

I agree with your original point. The British obviously thought Hess was more valuable to them alive.