The present invention relates to a closure system for a bottle designed for commercial bottling of a beverage or liquid food, preferably a wine bottle. The closure system comprising a stopper having a stopper part for introduction into a mouth of the bottle and a head part for remaining outside of the mouth, the head part having a diameter which is larger than that of the stopper part. The closure system also comprises a sealing element which is separate from the bottle and from the stopper. The closure system is configured such that the sealing element is forced against the inner wall of a mouth of the bottle, upon introduction of the stopper into the mouth, bringing the closure system into a locked state, and the stopper part comprises interlocking means to engage with counterpart interlocking means on the sealing element. The said interlocking means are configured to permit bringing the closure system into an unlocked state by an action which comprises rotating the stopper with respect to the bottle. The stopper part of the stopper also comprises a holding means configured to form an interlocking connection with counterpart holding means of the sealing element, to hold the stopper in a secured position with respect to the sealing element when the closure system is in a preassembled state.The present invention also describes a method of preassembling the closure system for a bottle and a method of closing a bottle using the preassembled closure system.