As a lay person it was interesting reading the appeal judgement.
My totally informal and at times very wrongly worded / termed thoughts are:
The Cabin Crew initially won the argument that they were making. However the consequences of enforcing that argument would mean that BA would be unfairly disadvantaged and so BA's greater potential suffering won the day.
Some points / thoughts:
a) The Lady Judge found the way that that BA and the Unions were agreeing things between each other to be unusual and that really BA should have been managing rather than coming to a lot of agreements.
However it is the following that counted in the case.
b) There was a disputed Section 7 in an agreement. This needed examining to see if the individual bits in it were aspirational, (unenforcable and losable by a Cabin Crew member taking BA to court over a breach of the relevant point) or potentially enforceable and winnable by the Cabin Crew member if a breach was made, ie potentially contractable. (The other sections of the particular agreement were littered with enforcable and unenforceable.)
The Lady Judge initially concluded that the Cabin Crew were right and that the parts of the relevant section that they contested were enforceable.
Half-Time: Cabin Crew 1 BA 0
c) BA's turn and the judge then looked at a replay of the first half and realised that the impact of saying that the relevant bits were enforceable, could then lead to unfairness to BA and that this unfairness was never the intention of the original agreement.
(As an example if Cabin Crew Complements were enforceable in an individual's contract then it would give too much power to an individual Cabin Crew member if they refused to work when presented with a One Down situation.)
So she gave a point to BA and another as the disadvantage that BA would be in would be far worse than that of the Cabin Crew.
So overall it was:
Cabin Crew 1 BA 2
Victory for BA but a fair effort by the Cabin Crew.
(Yes I do know that it is more complex than I have written above.)