Indicating right causes exterior lights to go out...

[XJ_Driver]

I have a curious new fault with my exterior lighting: basically with the headlights on, if I then operate the RH indicator all of the exterior lighting (sidelights, headlights, tail lights) immediately goes out!

Gave me quite a scare earlier: preparing to overtake a big truck at 60 MPH on an unlit A road, I indicated to pull out and was suddenly plunged into complete darkness... Utter panic for a few seconds, then cancelled the indicator and my headlights were at once restored.

To begin with I didn't realize what had caused the lights to go out, but at the next roundabout I used the RH indicator again and exactly the same thing happened. Pulled over after that and tested the operation of the indicator switch: signalling right extinguished all exterior lighting including main beam headlamps. LH indicator unaffected.

I was about to condemn the indicator / lighting stalk on the steering column, when I thought to try turning the engine off and back on again - and at once normal service was resumed. So I guess that eliminates the stalk?

Has anybody come across this fault before? As ever, advice appreciated!