Thanks for replying Tim. I must say it is rather frustrating, not being able to isolate the problem by simple means. I have now established that the brake lights come on - sometimes immediately, other times after a number of hours - whether the car is locked or not. I suppose at the end of the day it's going to be down to one of the systems controlled by an electronic-cum-computerised circuit. We'll get there in the end!! Maybe I should update the post when resolved?