After leaving television production, he worked as a consultant for the Internet Archive, helping to preserve and provide public access to cultural and technological media, including Computer Chronicles and other technology programs.
The full archive of Computer Chronicles is online because Stewart put in the work to make that happen. He talks a bit about it (and Computer Chronicles in general!) in a 2013 interview with Leo Laporte on TWiT: https://youtu.be/WdtHS_X1ibgRIP Stewart – you’ve taught me a lot!
Some of the better quality video archives, too. Most of them have interlaced MPEG-2 versions available, although a handful of the older ones do unfortunately have incorrect field order set in the MPEG headers