We went through a process whereby one of the doctors who'd looked after my Dad actually admitted he'd made a mistake and referred himself into their process for dealing with errors. Case review I think it was called. We had a really good liaison officer who actually contacted us out of the blue, to tell us what had happened as we had no idea.
My Dad died during covid, due to complications that arose as a consequence of a mistake made by a consultant and then which subsequently were not picked up by other members of staff, with several 'reminders' basically being ignored because staff were too busy. Basically, they didn't stop some medication when they should have, and it had an impact on other existing health conditions, and ultimately led to his death, despite him actually starting to recover from covid.
We didn't in the end pursue it legally, but got a formal apology from the trust, and a written breakdown of the everything that has happened. We also asked that they took active steps to try to avoid it happening again. We were offered a meeting with the staff involved, but didn't feel it would achieve anything. My Dad was in his mid 60s when he died, and had a couple of other life limiting conditions, albeit that they were being actively managed before he had covid and was admitted to hospital.
It wasn't a fun process to go through, and there were no legal elements to it, as we decided not to pursue. Just hearing all the details of my Dad's treatment, what he'd said, conversations he'd had etc, was very sad and in some ways very distressing. It was during covid, so we couldn't visit at all, only literally as he was dying were we able to go to see him. I don't know really if we did the right thing? Had my Dad been younger we might have felt differently.