A coupling mechanism allowing for yaw motion between first and second vehicle body portions comprises first and second legs 11b which separately comprise first 13b, second 14b and third 15b pivotal couplings, each coupling having an axis of rotation in a direction substantially perpendicular to a direction of motion, the first coupling of each leg being arranged for coupling an upper end of the respective leg to the second body portion 120, the second coupling of each leg being arranged for coupling a lower end of the respective leg to the second body portion the third coupling of each leg being arranged for coupling the respective leg to the first body portion 110, the axis of rotation of the first coupling of each leg being translatable in the direction of motion, and the axis of rotation of the second coupling of each leg being translatable in the vertical direction. Also disclosed is a catch for locking the second body portion in a raised position
