Being forced on RAF by MOD bean counters because of the two fleet rule IIRC.
The issue is the A400 is not a like for like replacement of the Herc.
Its a politics clusterfeck as per usual.
Airbus designed the A400 as a strategic airlifter that would enable many European airforces that couldn't afford, and didn't need the expensive heavy lift strategic capabilites that buying C-17 would have given them.
UK
bought into this with view of buying A400 for that task and keeping the C130 for what it was good at, i.e tactical ops, which most of the existing European airforces were going to do (or buy C-27 for tact use)
However, because of our politicians getting our mil involved in Iraq2 and Afgan post 9/11, the RAF needed urgent strat lift, which is why we leased some C-17's.
What then happened was we clearly needed that strat lift capability for a lot longer (and with A400 now where to be seen on the horiz) we bought the leased C17's and ordered a couple more before the line closed down.
At that point common sense should have prevailed, and we should have withdrawn from our commitment to a A400 buy, and ordered half a dozen or more extra C17 to keep the line open, and that would have provided UK strat air lift, keeping C130 for the tact role which it excels at, and which A400 wasn't really designed for (it was not designed as a C130 replacement)
We didn't though (European politics took priority) and have now pretty much flogged to death our too small fleet of C17's (they are all the highest houred C17's in the world) and most likely as per E-3D fleet, they won't get any money spent on mid-life upgrade) and they will all get prematurely retired in X years time, leaving just a A400 fleet that can only do strategic lift and very limited tactical, because we have also got rid of our tact air C130 fleet.....our two fleet inventory being pretty much a two fleet strat fleet rather one of one of the other.
This is what happens when you let the lunatics run the asylum.