A method for sealingly closing a bottle, the method comprising the steps of: a) providing a cage, a closing stopper and a capsule, wherein: - said cage is substantially cup-shaped and comprises a side wall with i) an inner surface comprising an annular relief in the vicinity of a free edge of the side wall and ii) an outer surface comprising an upper annular spur and a lower annular spur, wherein the upper annular spur is in the vicinity of a closed base of the cage and the lower spur is substantially opposite to the annular relief; - said capsule is cup-shaped and comprises a side wall which terminates in a free edge, wherein said side wall of the capsule comprises an annular projection which is configured to cooperate with the upper annular spur of the cage during a final assembly step, and an annular cavity; - the inner surface of the side wall of the cage comprises an elastic retaining element for retaining the closing stopper in position; b) joining the stopper to the cage and the cage to the capsule, thus obtaining a preassembled closing assembly, wherein said step of joining the cage to the capsule comprises having the upper annular spur received in the annular cavity so that the cage is only partially inserted inside the capsule; c) aligning the preassembled closing assembly on the mouth of the bottle and exerting a pressure so as to sealingly close the bottle, wherein the preassembled assembly is fitted onto the bottle in such a way that the annular relief presses elastically against a side surface of the bottle collar and wherein the annular relief of the cage comes into contact with the side surface of the collar of the bottle before the stopper comes into contact with the bottle; and d) exercising a pressure directed downwards on the closing assembly such that the annular relief of the cage engages with the bottom surface of the collar, the annular cavity engages with lower annular spur and the closing assembly remains locked to the bottle. a) providing a cage, a closing stopper and a capsule, wherein: - said cage is substantially cup-shaped and comprises a side wall with i) an inner surface comprising an annular relief in the vicinity of a free edge of the side wall and ii) an outer surface comprising an upper annular spur and a lower annular spur, wherein the upper annular spur is in the vicinity of a closed base of the cage and the lower spur is substantially opposite to the annular relief; - said capsule is cup-shaped and comprises a side wall which terminates in a free edge, wherein said side wall of the capsule comprises an annular projection which is configured to cooperate with the upper annular spur of the cage during a final assembly step, and an annular cavity; - the inner surface of the side wall of the cage comprises an elastic retaining element for retaining the closing stopper in position; - said cage is substantially cup-shaped and comprises a side wall with i) an inner surface comprising an annular relief in the vicinity of a free edge of the side wall and ii) an outer surface comprising an upper annular spur and a lower annular spur, wherein the upper annular spur is in the vicinity of a closed base of the cage and the lower spur is substantially opposite to the annular relief; i) an inner surface comprising an annular relief in the vicinity of a free edge of the side wall and ii) an outer surface comprising an upper annular spur and a lower annular spur, wherein the upper annular spur is in the vicinity of a closed base of the cage and the lower spur is substantially opposite to the annular relief; - said capsule is cup-shaped and comprises a side wall which terminates in a free edge, wherein said side wall of the capsule comprises an annular projection which is configured to cooperate with the upper annular spur of the cage during a final assembly step, and an annular cavity; - the inner surface of the side wall of the cage comprises an elastic retaining element for retaining the closing stopper in position; b) joining the stopper to the cage and the cage to the capsule, thus obtaining a preassembled closing assembly, wherein said step of joining the cage to the capsule comprises having the upper annular spur received in the annular cavity so that the cage is only partially inserted inside the capsule; c) aligning the preassembled closing assembly on the mouth of the bottle and exerting a pressure so as to sealingly close the bottle, wherein the preassembled assembly is fitted onto the bottle in such a way that the annular relief presses elastically against a side surface of the bottle collar and wherein the annular relief of the cage comes into contact with the side surface of the collar of the bottle before the stopper comes into contact with the bottle; and d) exercising a pressure directed downwards on the closing assembly such that the annular relief of the cage engages with the bottom surface of the collar, the annular cavity engages with lower annular spur and the closing assembly remains locked to the bottle.