"Cardiff" conducted her last Armilla patrol in early 2003. During her time in the Persian Gulf, "Cardiff" prevented more than £2 million of illegal cargo from being smuggled out of Iraq, inspected 178 vessels, and seized more than 25,000 tonnes of oil. The destroyer was relieved by before the beginning of the Iraq War and returned to Portsmouth on 4 April 2003. In late 2003, the ship was involved in the annual Sea Days demonstration exercise, and in October was used for tests of QinetiQ's Maritime Tactical Network.