The Phantom FGR.2 (F-4M), as it is known in the RAF, is a land-based derivative of the naval Phantom FG.1. The lack of an extending nose-wheel, and folding radome were among the changes brought forward in the new type. British Phantoms used the Rolls-Royce Spey turbofan over the J79. A custom RWR was fitted later in the type's career, producing the distinct square at the top of the vertical stabilizer. Initially, the FGR.2 (fighter, ground-attack, reconnaissance) were multi-role fighters, but with the introduction of the SEPECAT Jaguar, the Phantoms reverted to the air-defense role exclusively.