The present invention relates to a fuel injector (101) for use in delivering fuel to an internal combustion engine. The fuel injector (101) includes a nozzle (105) having a valve needle (107) which is movable with respect to a valve needle seat (117). The valve needle (107) travels through a range of movement between a closed position and an open position to control fuel delivery through at least one nozzle outlet (109). The valve needle (107) cooperates with a needle sleeve (111) which is located in a piston guide (133). The valve needle (107) is movable relative to the needle sleeve (111) and the needle sleeve (111) is movable relative to the piston guide (133). The invention also relates to a method of operating a fuel injector (101); and a fuel injector control unit.