Watch your Trolley !
Once upon a time drivers of 'Twin-Sets' needed to give especial care to the fact that if they were trailer unit leading (as in this case) the trolleypole was mounted on the Motor unit and therefore quite a distance behind when it came to activating points (among other routine actions). Not a whiff of metric measurement on Blackpool trams ! The use of pantographs instead would not alter the distance issue of course.
The warning notice was definitely in the driver's line of vision at all times from the cab end of the trailer unit.