Other unions have "Full Time Officials", why not BASSA? You could understand militant members might welcome DH & Co., being appointed just to "stick one up" at BA.
In my (very limited) union membership in the 1950's* I always understood that the penultimate place for a local dispute to go was York, where dedicated full time officials of both unions and employers negotiated matters over a table before going "National". I am probably about 50 years out of date with union procedures because at the first opportunity, (i.e. when I changed my job) I left the union and never re-joined, being responsible for my own pay negotiations ever since.
* As 16 year old engineering apprentices we were strongly co-erced (i.e. forced) to join the AEU even though it was not quite a closed shop.