Brace yourself, the below video is not going to blow you away. It's more like Mother from Synchronicity than Cygnus X-1, but it's wild to see Neil and Stewart together, knowing how much The Police influenced Rush in the 80s. I guess it makes sense but I don't think I have ever seen those two in the same room, much less in a free-form jam situation.
Would have been interesting to be a fly on the wall but this video edit is close. Enjoy!