A releasable connector (10) for joining tubular members in a well bore. The connector (10) is a mating screwthread (38, 58) which is terminated on each member by abutting projections (24, 64), operating as a ratchet. This ensures torque is transmitted between the members in a uni-directionally manner so that make-up torque is never applied to the screwheads when torque is applied to the members. A running tool (12) and a method of setting a liner in a well bore is also described which incorporate the connector (10) so that the liner may be part of a drill string and is left cemented in place in the well, after drilling is complete.