Ah, the old London book. Always funny to see the old Universal Brotherhood flyer...
Despite that, I think the best reference is in SR3 - Dragons of the Sixth World, pages 56 ff. (London Book 1991, Dragons 2003).
The Majority of the Knights have nubian/african roots. Also, Celedyrs second spotting was 2041, flying over Nubia.
Over the Knights Celedyr sponsors archaeologists to play in the Nubian Desert a little bit Indian Jones, searching for remains of the "Nubozi". And not only colored potsherds.
Side Info: Orange Queen commented the article when People Watcher stated that he never heard something about the Nubozi because they died before "recorded civilization began".
In 2043 Celedyr, showed the leaders of the street gang some holy stones and the gang pledged their loyalty to him.
He sorted the gang out. The best to protect Caerleon, the others hold up the gang as recruiting spot and for special purposes.
According to People Watcher when the egypts took over the nubians some survivors escaped to Austria, Germany and...Brittany. However, it's up to you if you're willing to trust People Watcher.
The Knights are heavy in encryption, decryption and encoding of messages, in Caerleon have high numbers of Deckers, Riggers and the like (all pre '64). How much survived the crash is, to my information, unknown but the Knights still serve as his guards in Caerleon.