Just with all these vans getting nicked lately.
This is what I've always done.
With the two different vans I've had for wfp they have both had a factory immobiliser linked to a chip in the keys. I have to have my ignition on to run my pump (just the way I've always had it set up, cig' lighter socket)
For both vans I got a key cut BUT with no chip in it, just a key blank cut to fit the ignition. So this enables me to have the ignition on & still be able to lock the van BUT the van cannot be started with that key.
Now I know they can nick it without keys BUT I reckon the time it would take them to suss out what's happening would be enough to send them off before being caught as the engine will turn but not fire!