Classic driving lamps to spot lamps

I'm sure somebody said a while back that the driving lamps on the classic can be altered to come on without main beam by swapping the plug on the back of the switch with a spare one tucked behind the switch panel somewhere? I've searched the posts but couldn't find the thread.Anybody done this or know if its true.

Behind the switch you should have two spare wires, one is for the low beam circuit, replace the main beam wire from the back of the switch with this one.

A volt meter will confirm which wire it is as I can not remember the colour.

Lamps on US Range Rovers were wired to come on on low beam and could be used as fog lamps.