Again, I agree with 101917.
The complication in addition to the points made in 101917's last post, is that even Counsel will have different opinions about how the issue of DoJ/ Seniority, (only when Seniority = DoJ), will eventually be resolved in UK law. There are multiple perspectives - including political perspectives..............so many that spelling them out is beyond my typing skills. Even the "ring fencing" option is open to challenge.
There is one possible way through, which is an opinion from an Employment QC which I received, (about a slightly different issue, and she was a left wing QC, so might not be in tune with the current Supreme Court perspective). The Age Discrimination stuff was supposed to be "sorted" by employers by late 2011, as 101917 says.
However, the QC suggested to me that an employer undertaking a "major" change after then might be able to argue that they needed 5 years from the effective date of the change to sort out all the issues. Thus, BA might be able to do some sort of deal with balpa and resist any challenges to that deal for up to 5 years.......as they were "sorting it out". As 5 years is a lifetime in Employee Relations, maybe that would do........