The original hydraulically operated switch screwed into a brake line junction
The first mechanical switch arrangement used on rubber bumper RHD cars, and Mk2 North American spec.
The 75 and later North American spec (subsequently all LHD and then RHD) arrangement with the same switch but mounted behind the pedal box (RN Lewin). This arrangement was used as each market received dual-circuit brakes with servo, not until 1977 for RHD.
The very short actuator pin (arrowed) on this switch means it has to be quite precisely located for correct operation. Not far enough in the lights are on all the time, too far in and it restricts the brake pedal return, which can cause the brakes to jam on as the fluid heats up and expands. There have been reports of replacement switches of this type pinging apart as the crimp of the body to the plastic insulator is inadequate.
After a flurry of posts about a mechanical conversion, and some pretty clunky ones, I came up with my own