Abstract: A padlock comprising a body and shackle, the shackle having an end releasably securable in the body, the body having a casing, the casing housing a tamper alarm means and a lock means, the tamper alarm means including a power supply means, the casing having an aperture configured and arranged to receive the end of the shackle being securable in the aperture by way of the lock means, a portion of the casing being movable to enable access to the power supply means, movement of the portion of the casing being prevented by a retaining means which is only accessible for insertion or removal via the aperture in the casing configured and arranged to receive the end of the shackle.