Okay, so when I started my new job my previous employer of 3.5 years was asked to provide a reference.
I’ve not had any problems in current job (6 months in now): I enjoy it very much and get great feedback from team members and clients.
In my previous job, I was made redundant due to the company closing the office and I wasn’t willing nor (importantly) able to travel.
Truthfully, I soon discovered after starting the job that my immediate line manager was a nightmare (something other senior members of staff had commented his behaviour), but it didn’t stop me from working hard.
I covered his work during an extended period of absence for 5 months, during which time I updated several critical systems that could’ve cost the company a LOT of money if left outdated. I didn’t seek any increase in salary for doing his work (hey - pitching in is teamwork, right?), nor did I receive any thanks.
Over time, I developed health problems of my own, which impacted my ability to live my life as “normal” and limited some of the work I could do, for which I focussed on other parts of the job. In due course, when things weren’t looking any better & was diagnosed as having a chronic condition, I informed my employer that I considered myself to have the characteristics covered in the disability part of the equality act.
After that, during the last two years of my employment, I had no appraisals, no training and was given the rubbish jobs by my line manager. Needless to say, I didn’t enjoy this and my requests were just brushed aside, yet I still ploughed on & worked hard. During this time, he had a grievance raised against him for pushing a fellow (fantastic performer) colleague out of their job and treating them appallingly.
I understood at the time that my line managers boss (reference writer, RW) could see the situation for what it was (despite never doing anything about it) and would be ideal for providing me with a reference. I thought RW would be able to see what was me, what was the effect of my line managers toxicity and what was my health condition.
Oh, how wrong was I?
The reference received scored me low for many personal attributes and it said they wouldn’t employ me again. It made reference to my “health issues” that I had experienced, as a reason for the scoring.
AIBU to think that a reference shouldn’t cite a disability as the reasons for someone’s alleged poor performance, and that if they DID have a problem with my performance, that they should’ve actually said something while I worked there, perhaps in a performance review, or some sort of disciplinary-related pathway?
I feel like my hard work has been forgotten, e.g. the time I had off sick/appointments, I made up by working extra hours (...not that RW would ever know how late anyone stayed after work as he was the first to leave the office, after spending the afternoon booking his holidays online 
)
Although my current employer doesn’t believe the reference, it’s quite embarrassing that they've seen it and so disappointing that my trust was so badly misplaced.