Sub-let carpet worry

Amy asks:
(updated on Monday, September 18th 2017)

I sublet a room in a shared flat last year. In the dining room a friend dropped a tiny splash of coffee on the carpet. Unfortunately, in our attempt to clean it up the carpet developed a huge yellow circle a lot bigger than the original stain. We attempted to clean it several times before discovering online that with old carpets the underlay seeps up into the carpet when you put water on it and stains it.

I moved out and a few months later the other flatmates from the actual lease have also moved out, so the landlord is coming for an inspection. In regards to the carpet, who pays? Would it be covered by his insurance? If not, as he needs to re-carpet the whole house anyway, do I still pay a percentage? Also this landlord never fixed anything during my time there despite us telling him about stuff. They still have my bond.