To add to this, I recently contacted my former TOC about back pay. They seem pretty steadfast. (I resigned from a FirstGroup TOC in July 2023 in good standing.)
The entire reply reads: 'When the RMT offer was agreed, we were also informed that employees that left the company prior to the agreement being made on 30/11/2023 would not be entitled to the back pay. This is the industry’s decision on back pay and affects every employee that left the company prior to that date.'
By 'the industry's decision', I presume they mean something they, the RDG or the DfT have made up, otherwise they would have said the RMT had agreed it. Note also the passive voice – they 'were informed' by whom?
I'm in a real bind as I am no longer on the railway and, obviously, left the RMT when I resigned. My current union is in a totally different industry and will have no expertise whatsoever if the RMT refuse to help me, and will in any case refuse to deal with a matter predating my membership. I hope the RMT do help me, as I was an active member and stood on the picket line to win a pay rise I'm now being denied by what I presume is the employer's cynicism.
I will contact the RMT next week to see what they say. I probably won't bother with ACAS. If neither the RMT nor my current union won't help, I will look into pursuing the TOC using the legal cover on my home insurance. It's outrageous.