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 , 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 , 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. <EOS>