Brian Gaff explained :
Kind of reminds me of the Iron my granny bought from Arding and Hobbs, it had
a bayonet plug like the end of a light bulb and the instructions showed it
plugged into the overhead light in a kitchen. Do not remember the make now,
but can you imagine the uproar if one tried this today?

Not that unusual back in the day, few people had and wall outlets. You
could even buy BC double adaptors, so you could plug the iron in and
have the bulb lit. Many of the homes with socket outlets, probably only
had a single 5amp two pin in the whole house. I remember my dad running
an electric fire, radio, Christmas tree and later a TV via a multi way
adaptor from a 5amp two pin. If the fuse blew, rewire with an even
bigger wire :-)