Bear in mind Barry that a new generation of Morgan electrics came into being from 2014 onwards which certainly applied to Roadster and Plus 4, likely the 4/4 as well. The switches became electronically latching via a BCU (body control unit), toggling on or off with a single press. An LED within switch illuminated when it was turned on, at other times it illuminated in dimmed mode, hence my comments your extra switch is probably not connected.
The advantage of this form of latching was that any selection was dropped (with exception of hazards) when ignition switched off. Very helpful if rear fog lights or screen heat for example had been on immediately before.
