Abstract: A cap for a container having a screw threaded opening comprising an inner part (1) in the form of a screw threaded cap, an outer part (2), biased therefrom in a first, locking position, by means of resilient biasing means (3) located between the inner and outer parts, a projection (4) located on the inner part (1) and adapted to be received in an aperture (8) formed in the outer part (2), and a tamper-evident member (6) secured on the outer top surface of the outer part (2) such that it substantially covers the aperture (8), wherein on first removing the cap from the container the outer part (2) is moved into a second, unlocking position, against the biasing, the projection (4) being received in the aperture (8), and projecting therebeyond, such that at least a portion of the tamper-evident member (6) is ruptured.