Nothing personal old fruit, but I'm not really convinced by visible deterrents like these or extra ironmongery on the outside of the door.
I reckon these vans are fundamentally extremely easy to break in to, and while something like this may well persuade the casual ne'er-do-well to find a different target, if they think you are trying to protect something of real value inside they may well do considerable damage in attempting to get in to find out.
While I wouldn't go as far as to leave all the windows wide open and put the welcome mat out, it's probably easier to cope with someone having got in and turned the place upside down leaving the van relatively unscathed than it is to cope with busted windows, mangled doors and trashed paintwork.
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