Street traders since the 19th century (and perhaps earlier) sold seasonal goods (especially vegetables) from two-wheeled barrows.
London's banks and investment brokerages were, since their foundation, privileged enclaves of wealth and high social standing.
After modernisation in the 1980s they ceased to be preserves of class privilege, and Cockneys of proven ability were employed as traders; such staff might be sneered at as "barrow boys" by traditionalist bankers or brokers.
[3] Conventionally there are two barrow boys, one at each end of a horizontal stretcher (though it may be vertical) which may contain a casualty.
The barrow boys may operate on fixed or moving ropes, and guide the progress of the stretcher to safer ground.