Thanks for the detailed reply Garry. I'll have another look at the switch, from memory the pin was blackish. With the switch removed I would have expected the brakelight to come on, which it didn't. So this seems to point to a damaged wire somewhere along the line. Can the the switch be disassembled?  I did notice the the wire did not swivel in the housing as I removed the switch, so I am concerned that I may have wrung its neck.