BEWARE OF AMATEUR TRAFFIC CONTROLLERS
From the 1934 Wills Cigarettes 'Safety First' album.
"Beware of amateur traffic controllers, for even if they are working with the best of intentions, they are seldom competent to act in an emergency. As they have no official status it is not unlikely that the driver of the other vehicle will ignore their signals. Danger signals, however, given by ordinary members of the public should always be obeyed, for, even if the danger has been exaggerated by the giver of the signal, there is safety in obedience. All-clear signals, on the other hand, are best ignored. Assure yourself that all is well before proceeding."