A panel has a gypsum matrix, in which the following additives are embedded: glass fibre in an amount greater than 1 wt % relative to the gypsum and a synthetic polymeric binder in an amount greater than 2.5 wt % relative to the gypsum. The glass fibre and synthetic polymeric binder are present in a weight ratio of at least 2 parts binder to one part fibre. The amount of sand present in the gypsum matrix lies in the range 0-0.5 wt % relative to the gypsum. The amount of cellulosic fibre present in the gypsum matrix lies in the range 0-2 wt % relative to the gypsum.