Fixing an SD memory card with broken lock…

Turns out all you need is some Scotch tape.  For some reason I thought it was a more complex mechanism.  Essentially the modern equivalent of the tab you used to see on VHS tapes to prevent overwriting.  And similarly as I recall there were special holes to allow S-VHS to be written.

https://en.wikipedia.org/wiki/Secure_Digital
https://en.wikipedia.org/wiki/VHS
https://en.wikipedia.org/wiki/S-VHS

So yeah, all you need is a wee bit of Scotch tape.  Takes all of 10 seconds and your SD card should be writable again.