A reformer includes at least one reformer reactor unit (300) having a space-confining wall with external (307) and internal surfaces (306), at least a section of the wall and space confined thereby defining a reforming reaction zone (311), an inlet end (301) and associated inlet (302) for admission of flow of gaseous reforming reactant to the reforming reaction zone (311), an outlet end (303) and associated outlet (304) for outflow of hydrogen-rich reformate produced in the reforming reaction zone (311), at least that section of the wall (305) corresponding to the reforming reaction zone comprising perovskite as a structural component thereof such wall section being gas-permeable to allow gaseous reforming reactant to diffuse therein and hydrogen-rich reformate to diffuse therefrom.