The toot itself is from 2021, and links to a 2012 PDF* from the "ASPECT 2012 Conference (UK)", specifically

   2.10 strangaric - legacy train control system stabilisation.pdf

[*] Due to the website's interface, navigating directly to https://webinfo.uk/webdocssl/irse-kbase/ref-viewer.aspx?refn... seems to serve a web page that requires clicking through to request the PDF.