Freelander 1 HDC Warning Light needs resetting

Couple of weeks ago, had my Freelander 1 TD4 back in the garage after a clutch change as the HDC warning light had come on whilst I was crawling in traffic. It was checked by the diagnostic and all was ok, the warning light just needed resetting. They unplugged it and re-plugged it in and all worked well. Today it came on again while I was in a traffic queue. Stupid me forgot to ask the mechanic what was unplugged and where and yes it was a garage that specializes in Landrover.
Any idea what I need to unplug and where it is please?