An improved umbrella comprising: a shaft; a plurality of ribs spaced around the shaft arranged to be capable of extending outwardly of the shaft in a deployed condition; a canopy supportable by the ribs; and a tensioner comprising a filamentary material which extends around the perimeter of the umbrella, wherein the filamentary material is arranged to tension the perimeter of the umbrella and resist inversion of the umbrella by pulling a distal end of each rib towards the shaft when in the deployed condition.