Jetex
Nimrod MR2 is Government Furnished Equipment to the MRA4 programme. It is the design baseline, which is then modified. The contract will (or should) state "Qty x MR2 to be fed in at the following build standard". Initially the latter will have been the current ADA build standard, but as the actual standard of each tail number emerges the contract will change (at MoD cost). The process I describe is designed to minimise these changes and hence reduce cost escalation.