Alas, xe is deceased, but I knew a chemist to whom your "non-standard kettle lead" description would be fighting words.
Xe would *always* correct anyone who referred to anything other than C15(C16) as a "kettle lead"; and xe worked with computer programmers who mostly didn't know the difference and made that mistake *all the time* when plugging C13(C14) kit in.
Xe caught wise that I did it deliberately within his hearing. (-:
The fun part, discovered today, is that the relative *also* has an honest-to-goodness proper EN 60320 kettle lead, with the high temperature notch (not the connector that computer programmers think a kettle lead to be (-: ), buried deeper in the garage.
I cannot be sure that the relative has none that fit that, given recent discoveries, but the relative's kettle that xe uses every day has a captive lead, as modern kettles now have.
The lack of a kitemark implies to me that this connector has been hoarded since before I was born.
It does have the standard number embossed on the plug, although it is worn and very difficult to read.
The relative has kept a non-kitemarked BS3283 kettle lead just in case xe might need it.
The relative has no working old electric kettles, and #BS3283 was withdrawn as an electrical standard three decades ago.
JdeBP