I've received requests from the British Library to allow my Knight's Tour Notes and Mayhematics websites to be "archived". I think this is a result of requests sent to them by John Beasley with regard to the archiving of the Chess Variants material and the BCVS site.
The address of the archive is: http://www.webarchive.org.uk/ukwa/. I've received emails acknowledging receipt of the online forms that I filled in, but I expect it will be some time before the sites actually appear in the archive. I took the precaution of removing some of the illustrations from the Biographies section of the Mayhematics site, in case they do not meet the copyright requirements.