Technical Reversing light switch on a 1995 2.5TD Ducato

[MadMickfiat]

Hi all
The reversing light on my Swift 630 isn't working when I put it into reverse anymore. The bulb and fuse are ok so I suspect the switch. Can anyone tell me where it is and how to check it please?
It has a 5 speed gearbox.

 

[varesecrazy]

Probably poking out on the rear of gearbox

 

[Communicator]

Test switch for continuity, with reverse gear selected.