For safety I have fitted an electrical cut off switch that stops the engine and isolates the car from the battery. The battery is in the boot, in its original tray, and has a positive lead running down the left hand side of the transmission tunnel and then up to two distribution studs, the switch cuts into this and sits nicely behind the gear selector.

There are two wires near the battery, which feed the engine management and fuel pump circuits, so I cut them and put in new wires from the cut off switch. Next I ran a new wire from the lower part of the switch to feed the ignition circuit and connected the alternator protection resistor. The regulations say that the cut off switch must isolate the vehicle’s electrics and cut off the engine. If the switch is activated when the engine is revving hard it will have enough inertia to carry on for a couple of seconds, and the alternator will continue to run. An alternator’s regulator cannot function without current flowing out of it, which it cannot do in an open circuit, so the voltage will rise, meaning the unit’s rectifier diodes will explode. The protection resister gives the alternator a small load allowing the regulator to work.