AFAIR (not always guaranteed :-)), that's correct. Which is why we used
to have bayonet adapters that could plug into pendant lighting sockets
in place of a bulb, and why we also had what amounts to a T-piece or
splitter, to allow both the bulb and the adapter to coexist. I think I
I remember those T adapters. 2 bayonet sockets to one plug. Often one
of the bayonet sockts was switched. Mostly by a button that slid through
the adapter, red on one side (press for on) black on the other (guess),
I did once see one with a cord (as in bit of string, not electric cable)
coming out the side which you pulled to switch the controlled socket
I have also seen (and probably still have somewhere) adapters to plug
a 2 pin 5A plug into a bayonet socket. What I have never seen is a T
adapter to go into a bayonet socket with one bayonet lampholder
and a 2 pin 5A socket.
Other oddities include a wooden bayonet plug (still have one, will
not use it) and a bayonet plug where the business end slid back
inside turning it into a 2 pin 5A plug.
-tony