Believe me XJs take ME about 60 seconds to steal, a professional would be done in 30 seconds no matter what your doors are. you'll just slow them down having full doors for 6-8 seconds.

Flat bar with a hook on the end to unlock your doors through the window, then a screw driver and a hammer will start the XJ, no need to hotwire.

I've lost my keys before... thats why I know.

 

^ just like all GM cars from the 80's and early 90's. Some people don't realize XJ's use GM columns that everyone knows how to steal. I can start my camaro with a bobby pin or anything small enough to stick in there without messing it up