Previously, the Royal Air Force had gathered signals intelligence with three Nimrod R1 aircraft. When the time came to upgrade the maritime Nimrods to MRA4 standard, Project Helix was launched in August 2003 to study options for extending the life of the R1 out to 2025. The option of switching to Rivet Joint was added to Helix in 2008, and the retirement of the R1 became inevitable when the MRA4 was cancelled under the UK's 2010 defence review. The R1's involvement over Libya in Operation Ellamy delayed its retirement until June 2011.