Sounds like a curly one there mate.
I find it strange that the Buchholz relay never tripped, I was under the impression that that was what they were designed to do in a fault like this.
This sort of thing is what I used to fear all the time with HV work, as in resetting and re-energising transformers, you just never know what is about to go wrong, you can test until the cows come home, but the real proof is when the supply goes back on.
I've been lucky sometimes and un-lucky other times, being unlucky is really hard on the nerves.
I hate the use of knife-links as a temporary Band-aid during upgrades, it's either fuses or nothing with me.
I can't wait to see the pics, when they arrive here, should be good.
BTW mate, hope you had a relatively nice, quiet (Faults and Fires-wise)Xmas/New Years break.