A surgical system comprising: at least two modular units, comprising a first modular unit and a second modular unit, each modular unit comprising: a surgical arm; and a motor unit comprising actuation elements configured for actuating movement of said surgical arm, said motor unit configured to be operably attached to said surgical arm, said motor unit defining a long axis; said motor unit comprising a housing; wherein the motor unit of said first modular unit is configured to be aligned adjacent the motor unit of said second modular unit, wherein a longitudinal face of said motor unit housing of said first modular unit comprises a connection geometry suitable for connecting said longitudinal face of said motor unit housing to a longitudinal face of said motor unit housing of said second modular unit; characterized in that said motor unit of each of said first and second modular units is operably attached to the respective surgical arm via an elongate recess defined in a longitudinal face of said motor unit housing; said elongate recess shaped and sized to removably receive an elongate portion of said surgical arm; wherein only when said surgical arm portion is received within said recess, said actuation elements contact said surgical arm to operably attach to the surgical arm, said surgical arm being mechanically held in place by one or more holding components and extending from a distal face of said motor unit housing, in parallel to said long axis of said motor unit. at least two modular units, comprising a first modular unit and a second modular unit, each modular unit comprising: a surgical arm; and a motor unit comprising actuation elements configured for actuating movement of said surgical arm, said motor unit configured to be operably attached to said surgical arm, said motor unit defining a long axis; said motor unit comprising a housing; a surgical arm; and a motor unit comprising actuation elements configured for actuating movement of said surgical arm, said motor unit configured to be operably attached to said surgical arm, said motor unit defining a long axis; said motor unit comprising a housing; wherein the motor unit of said first modular unit is configured to be aligned adjacent the motor unit of said second modular unit, wherein a longitudinal face of said motor unit housing of said first modular unit comprises a connection geometry suitable for connecting said longitudinal face of said motor unit housing to a longitudinal face of said motor unit housing of said second modular unit; characterized in that said motor unit of each of said first and second modular units is operably attached to the respective surgical arm via an elongate recess defined in a longitudinal face of said motor unit housing; said elongate recess shaped and sized to removably receive an elongate portion of said surgical arm; wherein only when said surgical arm portion is received within said recess, said actuation elements contact said surgical arm to operably attach to the surgical arm, said surgical arm being mechanically held in place by one or more holding components and extending from a distal face of said motor unit housing, in parallel to said long axis of said motor unit. <EOS>