A surgical system comprising: at least two modular units, the modular units each comprising: a surgical arm; and a motor unit configured for actuating movement of the surgical arm, the motor unit configured to be operably attached to the surgical arm, where a first face of a motor unit housing generally defines a plane which is at an angle of 60-120° to a long axis of the surgical arm; wherein the motor unit is configured to be aligned adjacent a motor unit of at least one second modular unit; wherein a second face of a housing of the motor unit generally defines a plane which is at an angle to the first face and which comprises a connection geometry suitable for connecting the housing of the motor unit to a housing of the motor unit of the second modular unit.