series 3 run switch

[jay_clierk]

on my land rover series 3, there is a switch, next to the spedometer that seems to be unprofessionally fitted. to switch the engine off, i flick this switch and it stops, then in turn the key off. i think the switch cuts off the fuel supply but im not sure. what does it really do and why is my landie so much noisier than everyone else's? does this switch have anything to do with it?

[AllYourBase]

My guess is that this switch could be part of a retro-fitted alarm/immobiliser system.
If the car is imported from overseas, it could be the rear foglight retro fit swtich.

[landie]

You sure it's not a diesel?