Freehold on flats and building insurance

I own a flat in a block of 4, all have their own entrance, we brought the freehold about 4 years ago, so the question is should we have a single buildings insurance for all 4 flats or should we all have our own insurance.
Just say the worst happened and it all burned down then we find out one flat has no insurance how do the others 3 flats stand

single building insurance and split cost 4 ways AS with all repairs to structure

Agree with Colin3 (fully)