Thank you, I'm still trying to catch up the down time on Monday and subsequent lack of sleep through the night wiped me out last night so effectively I'm running two days behind on posts and comments!

Basically a fork is as you say when then blockchain divides and the newer version renders the older one incapable. In this case the problem was we are preparing for a fork on the 25th for V20, but this error caused it to happen early and without consensus - so it could not be allowed. When it occured only the Witnesses running V20 could sign blocks, but with so many still on V19 who were trying but failing to sign blocks it caused the blockchain to become unmanageablely unstable. It stopped to protect itself, a solution to the problem was found and it restarted.

I think a video hangout on the whole Witness process would be awesome, we definitely should try to do that. If you have Discord grab me on there c0ff33a / Deranged [Witness]#7845