A stent device delivery system, comprising: a stent device pusher comprising an inner catheter, a radially self-expandable stent device and an outer sheath, the stent device comprising a lumen extending longitudinally therethrough, the stent device pusher comprising protrusions (12, 22) with axially extending spaces (14, 24) between them, the stent device being constrained in a radially contracted state by the outer sheath so that the protrusions of the stent pusher engage an inner surface of the stent device at positions axially distributed along the stent device, wherein the protrusions deform the stent device such that portions of the stent device extend radially inwardly axially between the protrusions to provide a form fit between the stent device pusher and the stent device, wherein the stent device comprises an inner cover providing a layer covering an inner surface of a tubular frame of the stent device, and wherein the protrusions deform the inner cover to provide a form fit between the stent device and the stent device pusher; characterised by a tacky material axially distributed along the stent device and providing a tackiness between the stent device pusher and the inner surface of the stent device, wherein the tackiness and the engagement of the protrusions with the inner surface of the stent device serve to resist axial movement of the stent device relative to the stent device pusher as the outer sheath slides axially over the stent device and the tacky material is such that it allows the stent device to peel from the tacky material and expand to a radially expanded state as the outer sheath slides axially over the stent device to unconstrain the stent device, wherein the tacky material provides a tacky interaction with the inner cover, and wherein the protrusions form a tacky interaction with the inner surface of the stent device by way of the tacky material, wherein the protrusions form a helix extending along the length of the stent device, the helix being formed by a wire being helically wrapped about the inner catheter and being adhesively bonded to the inner catheter with an adhesive material, the adhesive material also serving to provide a tacky interaction between the protrusions and an inner surface of the stent device. a stent device pusher comprising an inner catheter, a radially self-expandable stent device and an outer sheath, the stent device comprising a lumen extending longitudinally therethrough, the stent device pusher comprising protrusions (12, 22) with axially extending spaces (14, 24) between them, the stent device being constrained in a radially contracted state by the outer sheath so that the protrusions of the stent pusher engage an inner surface of the stent device at positions axially distributed along the stent device, wherein the protrusions deform the stent device such that portions of the stent device extend radially inwardly axially between the protrusions to provide a form fit between the stent device pusher and the stent device, wherein the stent device comprises an inner cover providing a layer covering an inner surface of a tubular frame of the stent device, and wherein the protrusions deform the inner cover to provide a form fit between the stent device and the stent device pusher; characterised by a tacky material axially distributed along the stent device and providing a tackiness between the stent device pusher and the inner surface of the stent device, wherein the tackiness and the engagement of the protrusions with the inner surface of the stent device serve to resist axial movement of the stent device relative to the stent device pusher as the outer sheath slides axially over the stent device and the tacky material is such that it allows the stent device to peel from the tacky material and expand to a radially expanded state as the outer sheath slides axially over the stent device to unconstrain the stent device, wherein the tacky material provides a tacky interaction with the inner cover, and wherein the protrusions form a tacky interaction with the inner surface of the stent device by way of the tacky material, wherein the protrusions form a helix extending along the length of the stent device, the helix being formed by a wire being helically wrapped about the inner catheter and being adhesively bonded to the inner catheter with an adhesive material, the adhesive material also serving to provide a tacky interaction between the protrusions and an inner surface of the stent device.