Sam at BLAGA rabbit hole today led me once again to Richard Gregory's useful website, which has been down the last few times I've tried.
Check out these two series of posts at the heart of it:
The English Signwriting Tradition: https://www.signpainting.co.uk/craft/
Letters Potent: https://www.signpainting.co.uk/lettering/
I've taken the liberty of downloading every page to my computer as the Wayback Machine copy doesn't look to be working as it should.
cc @internetarchive