ive got a toad alarm and a security post behind the car which i extended downwards by welding more box section and bits sticking out of the sides into a good amount of concrete which is poured all round it then paving slabs over the top.
a decent padlock is a must though, they are normally the week point of these posts.
just undo the padlock and lift the post out every time you take the car out.
you could probably stick a chain around it and drag it out with a bigish van, but you aint gonna do it quickly and quietly, plus the car is fairly well boxed in with other vehicles most nights.