We used to have a great HR team originally, really fair on both sides, excellent. The head of HR retired and we got someone who was truly appalling, rude, indiscreet, all smiles to management but could be dreadful to staff. Gradually the good team left, and the head recruited in their own image. It was toxic.
We went through several bouts of restructuring and redundancies during my time at the firm. Thankfully I survived all of them, especially as at one point DH had been made redundant and I was carrying the mortgage and bills on my own. My boss had a bit of a temper on him and could be monstrous at times (nothing I couldn't handle) but one day I just leant back in my chair and said to my workmates that he was being such a pain I wished they had made me redundant. One of the HR team was passing behind me and did no more than go straight to my boss, and their boss and told them what I'd said.
HR manager went to my boss and asked him if he wanted to facilitate this, I was called in by my boss who asked me about it, and then I had to go and see the HR manager. Several frustrating meetings just to explain that someone had taken an off the cuff remark as gospel.
This was just an indication of the sort of thing they did. Several colleagues had overheard conversations represented as gospel, personal information disclosed outside of HR etc which caused problems between PAs and their bosses, between team members. It was dreadful.
It all came to a head and the whole HR team was restructured, but then management in their wisdom outsourced the whole HR function to the same company as they used for their accounting which was all well and good, except they were in India, and not much better than the UK team to be honest.
Sorry this post is so long, but just wanted to give my experience of HR.