The invention resides in a hand-held medicament delivery device which comprises a housing containing a first electrical circuit and a battery, a medicament delivery mechanism, and a protective cap releasably securable to the housing. The housing also includes a contactless switch and the cap a switch actuator. The switch is operable between an on state in which the first electrical circuit is connected to the battery and an off state in which the first electrical circuit is disconnected from the battery. The invention also resides in a method of controlling power in a hand held medicament delivery device comprising the steps of actuating a contactless switch in the housing by an actuator in a housing cap when the switch and actuator are in proximity, the actuation of the switch signalling to a microprocessor that the cap is on the housing, detecting the status of the device by the microprocessor, and only if the microprocessor determines the device is inactive, powering down the device.