A set comprising: - an endoscope with - - i) an elongated housing defining an elongated gripping portion having an internal passage and - - ii) an insertion portion communicating with said internal passage and having a distal end, - a work tool unit having a work tool controller and an elongated flexible manipulation tube with a treatment instrument at the distal end thereof, - said housing and said work tool controller having complementary engagement structures (7, 8) for releasably connecting said work tool controller to said housing with said manipulation tube received by said internal passage and said insertion portion, - said internal passage extending from a proximal end of said elongated housing and through said elongated gripping portion, said engagement structure of said elongated housing being at said proximal end thereof, wherein - said engagement structures (7, 8) being configured for preventing rotation of at least a base of said work tool controller relative to said housing releasably connected with said work tool controller, - wherein free rotation of said manipulation tube relative to said base is prevented, - said work tool controller being configured for advancing said manipulation tube received by said insertion portion when said work tool controller is connected with said housing from a retracted position to an advanced position relative to said insertion portion, - said manipulation tube having an inner cable, said inner cable being connected to said treatment instrument and being movable relative to said manipulation tube. - an endoscope with - - i) an elongated housing defining an elongated gripping portion having an internal passage and - - ii) an insertion portion communicating with said internal passage and having a distal end, - - i) an elongated housing defining an elongated gripping portion having an internal passage and - - ii) an insertion portion communicating with said internal passage and having a distal end, - a work tool unit having a work tool controller and an elongated flexible manipulation tube with a treatment instrument at the distal end thereof, - said housing and said work tool controller having complementary engagement structures (7, 8) for releasably connecting said work tool controller to said housing with said manipulation tube received by said internal passage and said insertion portion, - said internal passage extending from a proximal end of said elongated housing and through said elongated gripping portion, said engagement structure of said elongated housing being at said proximal end thereof, wherein - said engagement structures (7, 8) being configured for preventing rotation of at least a base of said work tool controller relative to said housing releasably connected with said work tool controller, - wherein free rotation of said manipulation tube relative to said base is prevented, - said work tool controller being configured for advancing said manipulation tube received by said insertion portion when said work tool controller is connected with said housing from a retracted position to an advanced position relative to said insertion portion, - said manipulation tube having an inner cable, said inner cable being connected to said treatment instrument and being movable relative to said manipulation tube.