Direct proof of use
Mastiff was documented in British service during the 2003 Iraq War through UK parliamentary and Ministry of Defence material. In an October 2007 Iraq statement, the Prime Minister described Mastiff as a patrol vehicle offering strong protection against mines and roadside bombs and said that 100 had already been bought and deployed in Iraq and Afghanistan.
The Ministry of Defence's 2008-2009 annual report separately captioned Mastiff vehicles as used in Iraq and Afghanistan during a period when UK forces were completing their Basra mission, supporting Iraqi security forces, and conducting withdrawal and transition tasks.
Sources: Hansard Iraq Statement Mastiff Order, MOD Annual Report 2008-2009 Mastiff
Timeline
In December 2006, a defence written answer described funding for 108 Mastiff vehicles as part of urgent operational force enhancements. By October 2007, the government publicly stated that 100 Mastiff patrol vehicles had been bought and deployed in Iraq and Afghanistan, and it ordered 140 more.
By 2008-2009, official MOD reporting continued to identify Mastiff among vehicles used in both Iraq and Afghanistan while UK operations in Basra shifted toward completion, training, support to Iraqi forces, and withdrawal.
Sources: Hansard Mastiff Procurement Answer, Hansard Iraq Statement Mastiff Order, MOD Annual Report 2008-2009 Mastiff
Operational role
The Iraq evidence supports Mastiff as a British coalition protected-mobility vehicle rather than as a main combat vehicle. Defense Advancement describes Mastiff 2 as used in Iraq and Afghanistan for patrols, convoy escort, and force-protection duties in response to the IED threat.
British Army equipment data describes Mastiff as a heavily armoured 6x6 patrol vehicle suitable for road patrols and convoys, fitted with Bowman radios, electronic countermeasures, additional armour, and armament options including 7.62 mm, 12.7 mm, or 40 mm weapons. That configuration matches the force-protection role described in the Iraq deployment sources.
Sources: Defense Advancement Mastiff 2, British Army Mastiff, Hansard Iraq Statement Mastiff Order