In order to create the right leg, I decided to mirror the joints in the left, rather than just reconstruct the whole thing from scratch. I did this by selecting the entire set of joints from the hip; and then selecting 'Mirror Joint' from the Skeleton menu.
Next, I mirrored the reverse control, using the same method. I added each set of controls to its own layer.
The last thing that I shall mention in this post are the locators; they were made by creating curves shaped like the letters l and r. I moved these to the left and right legs and then constrained them as pole vectors to the IK handles in the legs. They can now control the orientation of the knees.