The MRA4 was ultimately cancelled in 2010 as a result of the Strategic Defence and Security Review (SDSR), at which point it was £789 million over-budget and over nine years late.

No direct replacement was under development at that stage, with the roles intended for the MRA4 filled by existing assets such as the Type 23 Frigate and the Merlin helicopter.

As well as operational performance, the key criteria were cost and a short procurement timescale; these "ruled out a new design or adaption of an existing civil aircraft.

[3] As part of Lockheed's submission, the firm offered a formal guarantee of a 20 per cent workshare on all future export sales of its Orion 2000 while simultaneously lobbying for the US Navy to also procure the type.

[8] In May 1996, it was reported that bidders were considering self-funding their own early development costs in order to compensate for alleged funding shortfalls within the MoD's procurement budget; it was claimed that these funding shortfalls were due to differences between the original specification, which had envisioned as an off-the-shelf procurement without much in terms of development, and the increasingly extensive nature that the programme had progressively taken on.

[12] In July 1996, in response to the committee's decision, Lockheed Martin announced that it had reduced the cost of its Orion 2000 submission by 15 per cent amid a series of last-minute discussions held between Lockheed Martin President Norman R. Augustine, General Electric Company President Lord Weinstock, Secretary of State for Defence Michael Portillo and Deputy Prime Minister Michael Heseltine, seeking a 90-day interval to fully revise their bid.

Significant changes were involved in the remanufacturing process, including the installation of BR710 turbofan engines, the adoption of a larger and more efficient wing with 23% greater surface area, various new missions systems and avionics, and an extensively refurbished fuselage.

[6] The larger wing increased fuel capacity by 30% which, combined with efficient modern engines, allowed for unrefuelled endurance in excess of 14 hours.

The Searchwater 2000 MR radar was stated to have been capable over land as well as water; with the ability to have swept an area the size of the UK every 10 seconds.

[22] In December 2002, BAE Systems issued a shock profit warning due to cost overruns of the Nimrod MRA4 and the Astute-class submarine projects.

In the 2010 Strategic Defence and Security Review of the Armed Forces, the UK government announced the cancellation of the MRA4 on 19 October 2010 and consequently that RAF Kinloss, the intended base for the Nimrod fleet, would be closed.

[43] It has been reported that following the retirement of the Nimrod MR2 (in March 2010[44]), Russian submarines have been able to travel past the UK in international waters, but they could not be tracked because of the lack of suitable aircraft.

[43] In November and early December 2014 four maritime patrol aircraft operated by France, Canada and the United States were based at RAF Lossiemouth to attempt to locate a Russian submarine which had been spotted in British territorial waters off west Scotland.

In this respect the Strategic Defence and Security Review stated that the UK "will depend on other maritime assets to contribute to the tasks previously planned for [the Nimrod MRA4]".

"[51] According to Air Forces Monthly magazine, "significant aerodynamic issues and associated flying control concerns in certain regimes of flight meant that it was grounded at the time of cancellation and may not have been signed over as safe by the Military Aviation Authority."

The magazine also stated that the reason for the cancellation was that the RAF and Navy placed a higher priority on fast jets and frigates than on maritime patrol.