Nice - thanks for the article! If you considering picking up a small wheeler yourself, would strongly recommend looking at the Dawes Kingpin instead of the Twenty. It’s fillet brazed and comes with none of the 26 TPI proprietary Raleigh threading to worry about.
Been reading up on Banham and all things bike design related, particularly smaller wheeled bikes, this led me to look for 20s. I'm loving this:
https://www.ebay.co.uk/itm/VINTAGE-RALEIGH-TWENTY-BIKE-MODERNISED/333612655856?hash=item4dacdd24f0:g:oh4AAOSwsype05wu
Link to awesome article:
https://www.researchgate.net/publication/271991616_A_New_Class_of_Cyclists_Banham's_Bicycle_and_the_Two-wheeled_World_it_didn't_Create