DO NOT HANG ON TO A MOVING VEHICLE
From the 1934 Wills Cigarettes 'Safety First' album.
"Bicycles are made to carry one only. It is an offence under the Road Traffic Act to carry more than one person on a pedal cycle unless it is constructed or adapted for the carriage of more than one person (including the rider). "Trick-riding" like that illustrated is extremely dangerous. All overloading should be avoided, for its least harmful effect is the rapid wear of the tyres and bearings. Much more serious is the risk of the failure of an overloaded frame tube, which may collapse suddenly without warning, especially when travelling fast over indifferent roads."