In vivo failure of a helical stent graft is addressed by provision of reinforcingmaterial for the graft material in at least two (preferably three) separate sections,each section comprising a continuous integral piece of material, wherein eachsection of reinforcing material is in the form of a helix with a longitudinal axissubstantially parallel to the longitudinal axis of the tube. Thus leaks causedby unravelling of the reinforcing material are mitigated.
