bummer! you’ve gone and cracked it!
I doubt silverfish will be much help if you have had it resprayed, I’d get it repaired at a quality steel bike builder myself fella – it’s a mk1 sovereign built out of 853 and 725 reynolds steel, and nothing like the newer ones ( different tubes, different geometry, better dropouts, designed by Dave Weagle) as It’s the Long version with the 16.5″ seat tube
As far as I’m aware you are the third owner of that frame, as I bought it off jncarpenter forum member off mtbr – must be 5 or 6 years old
It’s a classic, get it fixed and continue to ride it/enjoy it, I’ve never ridden a HT as good as that one