Mr F - gun story goes something like:
1. Air Marshal takes decision that gun should be deleted on cost grounds from all Tranche 2 and Tranche 3 airframes.
2. Remainder of air force mutters darkly that AM is an idiot.
3. Effort to get gun back begins.
4. Beancounters informed that removing gun will mean either:
a. Need to rewrite FCS for UK only (very, very expensive, no OBE for beancounter who signs this off)
OR:
b. Production of a specially machined lump of metal to fill void left by gun to avoid (a) above (very expensive. Asssumption of automatic OBE for beancounter signing this off moves to amber on beancounters' balanced scorecards)
BUT
c. Installing gun (cheap) will obviate need for (a) and (b), thus original plan makes best fiscal sense (OBE balanced scorecard returns to green).
5. Beancounters therefore agree all airframes should have gun, but that the gun will be 'unsupported' (i.e. no ammo, etc, etc).
6. Evidence that gun is quite handy for CAS comes from early ops in Afg with F-14s & F-15s doing strafing runs for TIC. Beancounters persuaded to modify position so that 'cannon capability' can be restored quickly if needed. Some blah on MoD website about how pilots will train to use gun in work-up to deployment, although will not train in its use on regular basis.
7. Further evidence from Afg of utility of gun leads to then-AOC 1 Grp announcing that the gun will be supported in service, although beancounters appear to be reluctant to confirm or deny that money will be available. Open source info that 3 Sqn not currently planning to make use of gun capability for QRA, while 11 Sqn 'expected' to have this option when deployed.