A Key cap has fallen off. How do I refit it?

[Bicko]

How it went?

I haven't had time to try it - the washing machine needed more urgent attention!

Sorted!  I can love my Pinebook Pro again.
I did notice that one of the metal lugs/hooks was bent and there were some scratches near it.  I think it must have had some 'attention' during assembly.
In case anyone else attempts this and would like a hint; you absolutely must separate the keycap from the scissor mechanism first - don't attempt this with the scissor assembly still attached to the keycap (as I did), you haven't got a hope!
Thanks @bolinches  for sharing your experience... a big help!