A flexible coupling capable of transmitting moments and comprising a first member having a longitudinal axis (30) connected by at least three joints (27) to a second member (41) having a longitudinal axis substantially aligned with the longitudinal axis of the first member, the joints being circumferentially spaced apart about said axis, each joint comprising a first part (27) on one of the members and a second part (31) on the other member, the parts of each joint interfitting so that moments can be transmitted between said members by the joints and so that relative sliding and rotational movement can take place between the parts of teach joint, the joint parts on at least one of the members being flexibly arranged (41) so that the members may articulate relative to one another.