Ratchet and latch mechanisms

A device for the application of a preload between a subsea wellhead and a conductor housing, comprising an activating member, a support housing, a locking member, and means for securing the support housing relative to the wellhead, the activating member being moveable in an activating direction relative to the support housing, the activating member and the support housing including surfaces which engage the locking member so as to cause in response to movement of the activating member in the activating direction an inclined lateral movement of the locking member, said inclined lateral movement having a component parallel to the activating direction which is substantially smaller than the movement of the activating member, characterised in that one of the activating member and support housing carries a ratchet comprising a multiplicity of serrations which have a regular pitch in the activating direction and the other of the activating member and support housing carries at least two latches which allow the relative movement and can engage the ratchet to inhibit movement reverse to the activating direction, the latches each providing a respective multiplicity of discrete locking positions spaced in the activating direction for the ratchet and being positioned and arranged so that the discrete locking positions provided by one of the latches are positionally out of phase with the discrete locking positions provided by the other latch or latches.