A web-locking retractor comprising a spool (16) about which seat belt webbing is wound, the spool (16) being rotatably mounted on a spindle which is slidably mounted in a frame (12), at least one sensing mechanism (200) responsive to conditions indicative of a crash to cause the spool (16) to lock to prevent further protraction of the seat belt webbing, a web-clamping mechanism (46) operable in response to vertical movement of the spool (16), sensing mechanism (200) and retraction spring (180) relative to the frame (12), to clamp the seat belt webbing against further protraction of the belt, wherein vertical movement of the spool (16), sensing mechanism (200) and retraction spring (180) take place subsequent to locking of the spool (16). Preferably the spool (16) is supported for rotational movement on a spindle, the ends of which are received in a slot in the frame (12). This spindle may for example be one arm of a U-shaped needle (150), the other arm (154) of which is received in another slot in the frame (12).