The invention relates to a tamper-evident seal assembly for use with a locking mechanism, the locking mechanism including a sliding member 5 which is slidable between a locked position and an unlocked position, said sliding member having a transversely projecting peg portion 11. The seal assembly comprises a channel portion 20 defining in its base a longitudinally aligned slot 21 through which the peg portion 11 can protrude, and a disposable breakable seal member 22 which is longitudinally slidable in the channel portion. The seal member 22 has means 23 for engagement with the projecting peg portion 11, such that, in the unlocked position, the seal member can be placed in the channel portion and in engagement with the peg portion, the seal member then being slidable in the channel portion and engagement between the seal member and the peg portion causing corresponding sliding of the sliding member to its locked position. In this position retaining parts 24 of the channel portion prevent lifting of the seal member, whilst the engagement between the seal member and the peg portion prevents sliding withdrawal of the seal member, whereby the locking mechanism is held in the locked position until the seal member is broken.