A medicament delivery device (100) for delivery of medicament through a cannula (132) from a cartridge (10). The device comprises a first container (11) for storage of a first substance, a second container (12), and valve means for closing a distal end of the second chamber (12). The second container (12) is arranged coaxially with respect to the first container (11). A mixing element (304) is provided for causing displacement of the second substance into the first container (11) through the valve means in a mixing stroke. A release element (202) is provided for holding the mixing element (304) in an initial position and is operable to release the mixing element (304) to initiate the mixing stroke. There is a needle shroud (400) for shrouding the cannula, and removal of the needle shroud (400) from the cannula (132) causes operation of the release element (202).
