I remember a site with the Reyrolle plugs and sockets, there was a small difference, so you could plug in a fused plug in either socket type, but the unfused plug would only fit fused sockets. The unfused sockets were on a 32 amp ring, relying on the fuses in the plug, the pins were the fuses, and an electrician, we that's what he said he was, replaced them for the modern yellow type, so 32 amp from a 16 amp socket, we replaced with a version using a 16 amp MCB in the outlet.
However, I have also seen yellow 3 kW portable transformers, often with a 10 amp push to reset overload on the 230 volts side, so 2300 watt at 55 volts = 41.8 amps, how they are allowed I don't know, a real fire risk. And I have seen where 110 volt leads have been used one plugged into the next, so when a scaffold pole caused a short line 1 to earth, there was not enough current to trip the 10 amp overload, until the cable melted and a second short circuit happened. We were lucky the scaffold planks showed burn marks but did not go on fire.
Since using extension leads, we simply put them all in the bin, but if the cables had been installed, that would have caused a lot of work.
Today where I work, we have 110 volt bricks for festoon lighting, but power tools are in the main battery powered. If I was the safety officer I would ban yellow bricks, all transformers should have overloads on the output. I have simply never worked out how the yellow brick was ever allowed?