A container defining an interior volume, the container comprising: an opening through which the interior volume is accessible from outside of the container; first and second tag receiving holes (12, 13) extending between the interior volume and the outside of the container; a tag holder comprising first and second parts (17, 18) that are separable from one another; and a radio-frequency identification tag having a frangible part arranged when broken to cause the radio-frequency identification tag to cease functioning, characterised by a closure flap moveable between an unfolded configuration in which the opening is uncovered and a folded configuration in which the closure flap covers the first and second tag receiving holes (12, 13) towards the outside of the container and at least partially covers the opening, the closure flap having a sling, wherein the first part of the tag holder is insertable into the first tag receiving hole but not removable from the first tag receiving hole from a side of the first tag receiving hole located towards the outside of the container, and the second part of the tag holder is insertable into the second tag receiving hole but not removable from the second tag receiving hole from a side of the second tag receiving hole located towards the outside of the container, and, with the closure flap in the folded configuration and the radio-frequency identification tag mounted on the tag holder so as to extend between the first part and the second part, the radio-frequency identification tag is locatable in the sling with the first part of the tag holder inserted in the first tag receiving hole and the second part of the tag holder inserted in the second tag receiving hole, such that moving the closure flap to the unfolded configuration moves the sling away from the first and second tag receiving holes (12, 13) and causes the frangible part of the radio-frequency identification tag to break and the radio-frequency identification tag to cease functioning. an opening through which the interior volume is accessible from outside of the container; first and second tag receiving holes (12, 13) extending between the interior volume and the outside of the container; a tag holder comprising first and second parts (17, 18) that are separable from one another; and a radio-frequency identification tag having a frangible part arranged when broken to cause the radio-frequency identification tag to cease functioning, characterised by a closure flap moveable between an unfolded configuration in which the opening is uncovered and a folded configuration in which the closure flap covers the first and second tag receiving holes (12, 13) towards the outside of the container and at least partially covers the opening, the closure flap having a sling, wherein the first part of the tag holder is insertable into the first tag receiving hole but not removable from the first tag receiving hole from a side of the first tag receiving hole located towards the outside of the container, and the second part of the tag holder is insertable into the second tag receiving hole but not removable from the second tag receiving hole from a side of the second tag receiving hole located towards the outside of the container, and, with the closure flap in the folded configuration and the radio-frequency identification tag mounted on the tag holder so as to extend between the first part and the second part, the radio-frequency identification tag is locatable in the sling with the first part of the tag holder inserted in the first tag receiving hole and the second part of the tag holder inserted in the second tag receiving hole, such that moving the closure flap to the unfolded configuration moves the sling away from the first and second tag receiving holes (12, 13) and causes the frangible part of the radio-frequency identification tag to break and the radio-frequency identification tag to cease functioning.