The missile was designed to meet the RAF's requirement for a long range anti-armour weapon, allowing strike aircraft to attack tanks and armoured vehicles at stand-off range, replacing the BL755 cluster bomb. This requirement was issued following an assessment of the British military's performance in the Gulf War. GEC-Marconi (whose missile interests now form part of MBDA) was originally awarded the contract on 7 November 1996.
The programme ended up nearly 3 years late. The first ground firing of the Brimstone missile occurred in August 1999, followed by the first air-launched firing from a Tornado GR4 in September 2000. Clearance of the missile was delayed by 12 months due to the unavailability of a Tornado trials aircraft, as the RAF chose instead to rush the development of the Storm Shadow air launched cruise missile ahead of the Iraq war, but another delay of 6 months resulted from redesigning the autopilot for safe release at higher speeds. Over 2,000 missiles were produced.
The original Brimstone could not be used in Afghanistan as the rules of engagement required a "man-in-the-loop". Under an Urgent Operational Requirement in 2008, modifications were made to the seeker and software of over 300 existing missiles to create Dual-Mode Brimstone. The new missiles can be laser guided according to the STANAG 3733 standard as well as retaining the millimetre wave seeker; the pilot can select either mode from the cockpit or use both simultaneously. Laser guidance allows specific enemy targets to be picked out in cluttered environments, the mmW radar ensures accuracy against moving target.
The development and procurement of the original single-mode missiles cost £370m, a figure inflated by accounting charges relating to the delays. The development of the dual-mode version cost an additional £10m. The The Daily Telegraph reports that the dual mode missiles cost £105,000, which is comparable to the cost of the AGM-65 Maverick; the MoD quote only a gross book value of £175,000, which includes development costs as well as the purchase cost of the missile. Upgrading a single-mode missile to dual mode costs between £35,000 and £45,000 plus VAT, depending on quantities ordered.
In March 2010 Brimstone was selected as the basis for the RAF's requirement under the Selective Precision Effects At Range (SPEAR) Capability 2 Block 1 programme. The Demonstration and Manufacture (D&M) contract will increase the missile's performance "significantly", and convert the warhead and rocket motor to use insensitive munitions. Brimstone 2 will have an improved seeker, a more modular design and improvements to airframe and software for "an overall increase in performance with improvements in range and engagement footprint", including a "more than 200% increase" in maximum range. A five-release test campaign in October 2013 culminated in a successful strike against a pickup truck travelling at 70 mph (110 km/h) in a cluttered road environment and Brimstone 2 is planned to enter service on the Tornado in November 2015.
At the same time MBDA were awarded an Assessment Phase contract for SPEAR Capability 3 (formerly SPEAR Drop 2). This is specified to have a range of at least 100km, however the UK MoD and MBDA believe that they can achieve over 120km (62+nm). The weapon will make substantial reuse of Brimstone modules. The 2 m (6.6 ft) weapon will fly at high-subsonic speed using a turbojet and wing kit, and will feature a multimode seeker with INS/GPS guidance and datalink. The assessment phase will conclude with flight trials in 2014 on Typhoon. The missile is set to use the same Hamilton Sundstrand TJ-150 turbojet as the JSOW-ER. MBDA have shown artwork of a four-missile launcher on a single Typhoon weapon station, and four will fit with a Meteor air-to-air missile in each internal weapons bay of the F-35B.
MBDA has started testing a maritime variant called Brimstone Sea Spear for use against swarms of small boats. On 25 June 2012 a Tornado GR4 dropped a prototype that hit and sank a 6-metre inflatable boat travelling at 20 kts in sea state 3. The following month MBDA said that a viable system could be offered "within months"; the initial focus is on deployment from fast jets and surface launchers, MBDA is marketing it in the Gulf for installation on vessels down to 15 m. On 29 May 2013, MBDA conducted a salvo firing of three millimetric wave operational Brimstone missiles, launched from a fixed offshore platform, against a simulated attack formation of five targets representing FIACs (Fast Inshore attack Craft). The successful test firing demonstrated Brimstone Sea Spear’s ability to strike numerous individual targets. During the test one of the targets, a 15-m craft, was travelling at 20 knots. The Sea Spear competed with the Raytheon Sea Griffin missile for integration onto American Littoral combat ships. The Navy instead selected the AGM-114L Hellfire as a stop-gap missile for the LCS.