(Daniel) Mudstuff, have sent me a Mechlock™. Basically, the Mechlock™ is a hydraulic valve operated with a key.  It will immobilize the clutch system, when the key is not present.

This allows me leave the vehicle running when I am not in it, for instance to use the winch or during recovery.

It also helps me to sleep at night, knowing that even Thatcham, the industry tester for security systems, could not get through the Mechlock™.

Here are some photos of the fitting.  It was very cold that evening!

For the technical people out there, it was recommended by mudstuff that we mount the unit on it's side, not upwards as it is here.  however, we were short on pipe, and it was a bit tight down there! 

We had to make up new pipes, as we changed the standard location of the unit, as this was already being used for another unique fitting.  Here is the pipe after a session with the flange tool!  I always wanted to say that!

I hate electrics, They go wrong for the silliest reasons, and can take forever to diagnose.  fortunatley the wolf is fairly sparse when it comes to wiring, as can be seen here.