Op TELIC

Operation Telic (Op TELIC) was the codename under which all of the United Kingdom's military operations in Iraq were conducted between the start of the Invasion of Iraq on 19 March 2003 and the withdrawal of the last remaining British forces on 22 May 2011. The bulk of the mission ended on 30 April 2009 but around 150 troops, mainly from the Royal Navy, remained in Iraq until 22 May 2011 as part of the Iraqi Training and Advisory Mission. 46,000 troops were deployed at the onset of the invasion and the total cost of war stood at £9.24 billion in 2010.

Operation Telic was one of the largest deployments of British forces since World War II. It was only approached in size by the 1991 Operation Granby deployment for the Gulf War and the 1956 Operation Musketeer Suez Crisis deployment. It was considerably larger than the 1982 Operation Corporate in the Falklands War, which saw around 30,000 personnel deployed and the Korean War, which saw fewer than 20,000 personnel deployed.

Some 9,500 of the British servicemen and women who deployed on Operation Telic for the invasion and its aftermath were reservists, from the Territorial Army and from the Royal Auxiliary Air Force Regiment.

Notice that additional British forces were deploying to the region (large numbers of RAF personnel were already deployed in Kuwait, Turkey and elsewhere in the region on Operations Northern Watch and Southern Watch) was given in three separate Commons statements by Geoff Hoon Secretary of State for Defence. On 7 January, the deployment of naval forces and Royal Marines was announced. 20 January saw the land forces deployment announced and 6 February the air forces. They were ready in time for hostilities to start on 19 March. When compared with the deployment of forces prior to the Gulf War things proceeded a great deal faster, with the slowest deploying elements taking 10 weeks to get from base to combat readiness in the theatre.

...
Wikipedia