Abstract: The present invention relates to a fluid vessel insertion device comprising a) a puncture member arranged for location within a cannulation sheet and comprising an interior lumen; b) a retractor arranged to actuate the puncture member relative to the cannulation sheet in use between i) a first situation in which a distal end of the puncture member protrudes beyond an end of the cannulation sheet, and ii) a second situation in which the distal end of the puncture member is within the cannulation sheet; c) a chamber in fluid communication with an exterior of the device only via the lumen and distal end of the puncture member; and d) a sheet of material located in the chamber to prevent the proximal end of the puncture member from moving; wherein the distal end of the puncture member is configured as a puncturing end having a distal n end opening for insertion into a fluid vessel when in use, and wherein the retractor triggers retraction of the puncture member between the first and the second situation automatic