Fitted additional third brake light (3BL) inside rear screen.
Soldered on bullet connectors to live and earth wires supplied with light as they are very short.
Added extension wires from there to nearside rear lights. Connectors just pushed behind rear roof lining finisher and wires run behind trim all the way down to rear brake light.
Replaced existing single bullet connector, live feed to rear brake light, with double and connected 3BL live feed wire plus rear brake light wire. Added crimped on spade terminal to 3BL earth wire and fastened to bolt on light fitting. See photo.
Did have to modify the 3BL end housing to allow the lamp to swivel more to make 3BL show better from behind the car. (not 360 degrees rotation as stated.) Just filed a slot in the plastic end cap so the wires allowed more movement.
All seems good.