how old is it because if its newer than 2001 it most likely has efective one built in ....and if its older its not very easy to imoblise electricaly as the electrics are simple and easy to hot wire.. its best to go for a physical thing like a lock or posts in the ground , tracker might help if it was stolen and discourage theft if the buggers think its got one however they can find them and disable !!! . post code on the roof is also a good idea.. Hope this helps
) of thieves sitting on motorway bridges and spotting vehicles to steal - also nothing to stop them painting over roof and postcode as a quick-fix. Want to discourage theft as well as hopefully get it back if it is nicked! Never owned something so nice in my life and am happy to spend on the deterrant. 
You need to check if its a old euro 2 if it is it is the old mecanical diesel pump.. or euro 3 electronic pump and a speed limiter im not sure on a MAN but most, iveco merc, daf have a chip key imobliser on the electronic ones... you need to find out if it has a chip in the key then its going to be harder to steal it without keys , if not then you just need to do what the insurance wants...It's 2003, apparently it needs a Thatcham Cat 2 immobiliser fitted for insurance co to cover it for theft and builder does not think it has one built in. I know nothing about the spec of chassis cabs and have no reason to doubt him, but am happy to take advice. It's a MAN LE 7.5 tonne if that helps.
Can't put posts in ground as open-plan car park on livery yard. Gate is secured with padlock but nothing bolt croppers can't tackle, reasonably secure as someone on site 24/7 with random comings and goings at all hours in an unpredictable fashion due to nature of their work. Not putting post code on roof due to (possible urban legend
Will put steering wheel lock on, can't fit wheel clamp due to skirts, has battery isolator, has ramp which can be padlocked shut.