Glow Plug controller, or?


Hi all, I´m putting a DL52 engine in a Series 3 Land Rover. There´s some kind of control device attached with two black wires/tabs to the glow plug rail. The device is a plastic tube shaped, app 3" long/0,50" dia. Two wires, brown/white, both cut. What´s the purpose of this tube and how do I hook it up?

I´m assuming it´s some kind of control device, maybe connected to a "Glow plug indicator" bulb in the dash, to let me know when the plugs are heated. When checking the wiring diagram, there´s a "Glow plug controller", but can´t find any more info or pic.