A surgical instrument, comprising: a handle assembly supporting a first actuator (24, 26, 38) thereon; an elongated shaft extending distally from the handle assembly and defining a longitudinal axis (A-A), the elongated shaft including a proximal structural member and a proximal drive member, the proximal drive member operatively coupled to the first actuator such that manipulation of the first actuator induces movement of the proximal drive member relative to the proximal structural member; a modular end effector removably coupled to the elongated shaft, the end effector including a distal structural member and a distal drive member, the distal drive member operatively coupled to a pair of jaw members (32, 34) such that movement of the distal drive member relative to the distal structural member induces movement of the jaw members between an open configuration wherein the jaw members are substantially spaced to a closed configuration wherein the jaw members are closer together; and a separable joint defined between the elongated shaft and the end effector, the separable joint comprising: a laterally prominent portion (106a, 104a) and a laterally indented portion (106b, 104b) defined on each of the proximal and distal structural members and configured to interlock with one another such that the proximal and distal structural members resist longitudinal separation and permit separation in at least one lateral direction (E3, E4); and a laterally prominent portion (120, 132) and a laterally indented portion defined on each of the proximal and distal drive members and configured to interlock with one another such that the proximal and distal drive members transmit motion therebetween and permit separation in the at least one lateral direction; wherein the drive members are movable relative to the structural members to move the separable joint between a locked configuration wherein the drive members prohibit separation of the structural members and an unlocked configuration wherein the drive members permit separation of the structural members in the at least one lateral direction, wherein the end effector includes a knife selectively movable through the jaw members, characterised in that the separable joint includes separable and interlocking portions of a distal knife rod and a proximal knife rod, the distal knife rod operatively coupled to the knife to move the knife through the jaw members, the proximal knife rod selectively movable with respect to the structural members and with respect to the proximal drive member from the handle assembly. a handle assembly supporting a first actuator (24, 26, 38) thereon; an elongated shaft extending distally from the handle assembly and defining a longitudinal axis (A-A), the elongated shaft including a proximal structural member and a proximal drive member, the proximal drive member operatively coupled to the first actuator such that manipulation of the first actuator induces movement of the proximal drive member relative to the proximal structural member; a modular end effector removably coupled to the elongated shaft, the end effector including a distal structural member and a distal drive member, the distal drive member operatively coupled to a pair of jaw members (32, 34) such that movement of the distal drive member relative to the distal structural member induces movement of the jaw members between an open configuration wherein the jaw members are substantially spaced to a closed configuration wherein the jaw members are closer together; and a separable joint defined between the elongated shaft and the end effector, the separable joint comprising: a laterally prominent portion (106a, 104a) and a laterally indented portion (106b, 104b) defined on each of the proximal and distal structural members and configured to interlock with one another such that the proximal and distal structural members resist longitudinal separation and permit separation in at least one lateral direction (E3, E4); and a laterally prominent portion (120, 132) and a laterally indented portion defined on each of the proximal and distal drive members and configured to interlock with one another such that the proximal and distal drive members transmit motion therebetween and permit separation in the at least one lateral direction; wherein the drive members are movable relative to the structural members to move the separable joint between a locked configuration wherein the drive members prohibit separation of the structural members and an unlocked configuration wherein the drive members permit separation of the structural members in the at least one lateral direction, a laterally prominent portion (106a, 104a) and a laterally indented portion (106b, 104b) defined on each of the proximal and distal structural members and configured to interlock with one another such that the proximal and distal structural members resist longitudinal separation and permit separation in at least one lateral direction (E3, E4); and a laterally prominent portion (120, 132) and a laterally indented portion defined on each of the proximal and distal drive members and configured to interlock with one another such that the proximal and distal drive members transmit motion therebetween and permit separation in the at least one lateral direction; wherein the drive members are movable relative to the structural members to move the separable joint between a locked configuration wherein the drive members prohibit separation of the structural members and an unlocked configuration wherein the drive members permit separation of the structural members in the at least one lateral direction,