"MIG" wrote:

On the top deck of double deckers there used to only be one bell push,
at the top of the stairs.

I assumed that this was to stop people finding one by their seat and
being tempted to stay there, ie force them to already be on their way
out rather than delay the bus at the stop.

In RM days, this was often inconvenient for conductors, stuck issuing
tickets at the front of the top deck. They sometimes resorted to two loud
taps, with metal clippers, on a suitable surface above the driver, as an
improvised 'ding ding'.

How much of a view they had of the platform from that position is a matter
of conjecture........

Chris