Rumour and hearsay is that the MOD settled out of court for a couple of really big claims by Spec Aircrew to avoid a precedent being set of having either a huge rise in the bill for pensions or the tax man having to pay back 40% of flying pay for the last 7 years! The result is the Professional Aviator Spine in which the recipient no longer receives flying pay but is paid an enhanced salary. Once again this does not set a precedent for paying out back taxes or a pension including flying pay (its not a bad pension though provided you stick out for your full term).
I reiterate that the out of court bit is just a rumour, however bearing in mind the name of this site......
PS. Yellow Sun added his experience while I was typing my snippet. I bow to his experience and acknowledge that the rumours certainly did circulate! Its a good story tho!