A flexible-shaft surgical instrument comprising: a semi-rigid tube having a distal end and a proximal end, the semi-rigid tube comprising a plurality of links, the links including a male portion and a female portion, the male portion being inserted into the female portion of an adjacent link; a surgical device having an elongated portion with a distal end, a proximal end and an intermediate portion between the distal and proximal ends (40A, 40B), at least part of the intermediate portion being flexible, at least part of the surgical device being disposed within a hollow portion of the semi-rigid tube such that the plurality of links are aligned with at least part of the intermediate portion of the surgical device; a distal compression bearing that is provided on the surgical device at a position that is adjacent to the distal end of the surgical device, the distal compression bearing radially protruding from an outer surface of the surgical device; and characterised by a compression member that is movably attached to the surgical device at a position that is proximal to the proximal end of the semi-rigid tube, the semi-rigid tube being disposed between the compression member and the distal compression bearing, the compression member being distally movable relative to the surgical device to provide a compression force to the semi-rigid tube between the compression member and the distal compression bearing so as to compress the plurality of links together and rigidly lock the semi-rigid tube and the intermediate portion of the surgical device at a user-selectable predetermined bend angle, the compression member being proximally movable relative to the surgical device to release the compression force from the semi-rigid tube and thereby return the semi-rigid tube and the intermediate portion of the surgical device to an unlocked state. a semi-rigid tube having a distal end and a proximal end, the semi-rigid tube comprising a plurality of links, the links including a male portion and a female portion, the male portion being inserted into the female portion of an adjacent link; a surgical device having an elongated portion with a distal end, a proximal end and an intermediate portion between the distal and proximal ends (40A, 40B), at least part of the intermediate portion being flexible, at least part of the surgical device being disposed within a hollow portion of the semi-rigid tube such that the plurality of links are aligned with at least part of the intermediate portion of the surgical device; a distal compression bearing that is provided on the surgical device at a position that is adjacent to the distal end of the surgical device, the distal compression bearing radially protruding from an outer surface of the surgical device; and characterised by a compression member that is movably attached to the surgical device at a position that is proximal to the proximal end of the semi-rigid tube, the semi-rigid tube being disposed between the compression member and the distal compression bearing, the compression member being distally movable relative to the surgical device to provide a compression force to the semi-rigid tube between the compression member and the distal compression bearing so as to compress the plurality of links together and rigidly lock the semi-rigid tube and the intermediate portion of the surgical device at a user-selectable predetermined bend angle, the compression member being proximally movable relative to the surgical device to release the compression force from the semi-rigid tube and thereby return the semi-rigid tube and the intermediate portion of the surgical device to an unlocked state.