On 27th January 2022, Brent Smith led a walking tour of Letchworth for Probus, and has kindly agreed to share the notes of the tour - viewable as a PDF:

Probus Tour of Letchworth

Please note: none of the facts within the attachment have been verified and no responsibility is taken for their contents.
The article is copyright of the author and the Heritage Foundation and contains a restriction on copying any part of it