Blame the Army!
In 2002 the FRES User Requirement Document required a battlegroup to deploy at least x000nm with crew and mission essential equipment, and to be able to undertake operations within one hour of deplaning.
It was determined by a Studies Assumptions Group that the current UK air fleet could not deploy a C130 compliant FRES battlegroup within the CI4a timelines. That, the C130 envelope placed too stringent a constraint on FRES, so the most efficient means of strategic air transport of a FRES-equipped force and its combat supplies was considered to be by A400M and ‘other Future Large Aircraft’.
Therefore, DEC DBE (Direct Battlefield Engagement) selected A400M compliance as a system-level Key User Requirement for FRES, with C130 as (merely) a priority 1 requirement, Mobility and C2 roles being the priority for C130J compatibility. Priority 1 often falls into the you must be bloody joking category when it comes to approvals.
The pitfalls are obvious. The FRES URD was a beyond parody, and clearly wouldn’t be delivered within a decade of the notional In Service Date. And so it proved. (And it wasn’t DEC DBE’s top priority at the time anyway). The knock-on effects on other programmes, not least C130, were equally obvious. And managing such programmatic integration is quite difficult, and almost impossible if not resourced correctly. (Just because FRES slips, doesn’t mean dependencies get compensatory funding, which creates gaps). One of the assumptions made was that this would all be managed by a Service HQ department that had been shut down 15 years before, without replacement. The technical term is **** show.