fastening the door on with some of these might work for a bit till the thieves get wise and buy a suitable socket:
Pin Hex Countersunk Security Machine Screw
The pattern does seem to be if they can have it away, they will, if they can't start it they'll have the doors and if they can't get the doors off they torch it so if they can't have it, you can't either.
that was the way wiv expensive caravans round here a few years back.
ny next door matey on our local touristy site had his "hoby" knicked one night, police knew where it was, but said "if" they entered the pikeysite to try an get it back,
it would be torched there and then.
on the site I was on, we had 5 expensive vans go in one week!!!
mine was too old at 5`ish years of age...
...luckily so it seemed..
must say around here lately fingers crossed, no known landies are being nicked nor having doors stolen,
nor caravans going come to think of it...
(but I still fit my extra steering wheel lock on each night),
oh, and my 2 russells & lassa apso sleep nearly under the open window where landies kept...