28a - the answer seems to be STRINGER - I get STRING is a group of (polo) horses, and ER is our dear Mrs Huggett, but WTH does STRINGER have to do with "hack" please?...
This was the toughest puzzle I have seen for a very long time, and I've been doing it for years! 23A - Disturbing someone in hospital, ringing in *i*i*t*r 16D - Left wing's first half getting stuck...