A servo valve comprising: first and second nozzles ; and first and second piezoelectric actuators arranged to control fluid flow through the first and second nozzles respectively, wherein: a first fluid flow path is defined between the first nozzle and the first piezoelectric actuator ; a second fluid flow path is defined between the second nozzle and the second piezoelectric actuator ; and the first and second piezoelectric actuators are arranged such that applying a voltage to the first and second piezoelectric actuators causes a change in dimension thereof, which acts to open or restrict said first and second fluid flow paths respectively; the servo valve further comprising: a servo valve housing including a pair of nozzle cavities , each housing a respective nozzle and piezoelectric actuator , wherein the piezoelectric actuators are retained in the nozzle cavities by contact between a first axial end of each piezoelectric actuator opposite a second axial end facing the nozzle and a wall defined by the respective nozzle cavity ; characterised in that : the wall is a common wall shared by the first and second nozzle cavities and separating the first and second nozzle cavities . first and second nozzles ; and first and second piezoelectric actuators arranged to control fluid flow through the first and second nozzles respectively, wherein: a first fluid flow path is defined between the first nozzle and the first piezoelectric actuator ; a second fluid flow path is defined between the second nozzle and the second piezoelectric actuator ; and the first and second piezoelectric actuators are arranged such that applying a voltage to the first and second piezoelectric actuators causes a change in dimension thereof, which acts to open or restrict said first and second fluid flow paths respectively; a first fluid flow path is defined between the first nozzle and the first piezoelectric actuator ; a second fluid flow path is defined between the second nozzle and the second piezoelectric actuator ; and the first and second piezoelectric actuators are arranged such that applying a voltage to the first and second piezoelectric actuators causes a change in dimension thereof, which acts to open or restrict said first and second fluid flow paths respectively; the servo valve further comprising: a servo valve housing including a pair of nozzle cavities , each housing a respective nozzle and piezoelectric actuator , wherein the piezoelectric actuators are retained in the nozzle cavities by contact between a first axial end of each piezoelectric actuator opposite a second axial end facing the nozzle and a wall defined by the respective nozzle cavity ; a servo valve housing including a pair of nozzle cavities , each housing a respective nozzle and piezoelectric actuator , wherein the piezoelectric actuators are retained in the nozzle cavities by contact between a first axial end of each piezoelectric actuator opposite a second axial end facing the nozzle and a wall defined by the respective nozzle cavity ; characterised in that : the wall is a common wall shared by the first and second nozzle cavities and separating the first and second nozzle cavities . <EOS>