A roof tile system, comprising: a first roof tile and a second roof tile, the first and second roof tiles each comprising: a first attaching means, the first attaching means for attaching the first roof tile to a second roof tile when the first roof tile and the second roof tile are arranged together on a roof; and a flange extending from a first end portion of the respective first and second roof tiles, the flange comprising an upper surface and a lower surface, wherein, as the flange extends, the profile of the upper surface increases at a shallow angle to a peak then drops sharply to form a deep recess and then rises again to the upper end of the roof tile; and a tile holding device for fixing to the roof, the tile holding device comprising a base portion, a back portion and an engagement portion, the base portion and the engagement portion extending from the same side of each end of the back portion at a substantially perpendicular angle, wherein as the engagement portion extends, it curves towards the base portion and wherein the curve forms an upper arc and defines a channel between the engagement portion and the base potion, wherein the tile holding device is arranged to enable movement of the first roof tile with its flange engaged in the tile holding device, from a first orientation to a second orientation by a pivoting action about the flange and the degree of curvature of the upper arc allows the engaging flange to be inserted between the engagement portion and the base portion when the plane of the tile is orientated at the first orientation with respect to the plane of the base portion and the deep recess is engageable with the engagement portion to prevent insertion or removal of the flange when the first roof tile is orientated at the second orientation, to inhibit lifting of the first end portion of the first roof tile away from the roof. a first roof tile and a second roof tile, the first and second roof tiles each comprising: a first attaching means, the first attaching means for attaching the first roof tile to a second roof tile when the first roof tile and the second roof tile are arranged together on a roof; and a flange extending from a first end portion of the respective first and second roof tiles, the flange comprising an upper surface and a lower surface, wherein, as the flange extends, the profile of the upper surface increases at a shallow angle to a peak then drops sharply to form a deep recess and then rises again to the upper end of the roof tile; and a first attaching means, the first attaching means for attaching the first roof tile to a second roof tile when the first roof tile and the second roof tile are arranged together on a roof; and a flange extending from a first end portion of the respective first and second roof tiles, the flange comprising an upper surface and a lower surface, wherein, as the flange extends, the profile of the upper surface increases at a shallow angle to a peak then drops sharply to form a deep recess and then rises again to the upper end of the roof tile; and a tile holding device for fixing to the roof, the tile holding device comprising a base portion, a back portion and an engagement portion, the base portion and the engagement portion extending from the same side of each end of the back portion at a substantially perpendicular angle, wherein as the engagement portion extends, it curves towards the base portion and wherein the curve forms an upper arc and defines a channel between the engagement portion and the base potion, wherein the tile holding device is arranged to enable movement of the first roof tile with its flange engaged in the tile holding device, from a first orientation to a second orientation by a pivoting action about the flange and the degree of curvature of the upper arc allows the engaging flange to be inserted between the engagement portion and the base portion when the plane of the tile is orientated at the first orientation with respect to the plane of the base portion and the deep recess is engageable with the engagement portion to prevent insertion or removal of the flange when the first roof tile is orientated at the second orientation, to inhibit lifting of the first end portion of the first roof tile away from the roof.