Checking for alignment; both of these arms are straight.
It is not uncommon to find that your classic Mini has a bent rear suspension trailing arm. Symptoms of this are the Mini crabbing down the road, having excessive toe-in or toe-out at the back, or excessive positive camber at the rear.
To determine if one is bent, or which one is bent, first remove the rear trailing arms from the car. Then slide the pivot shaft from one arm into the other, so that the one shaft is going through both arms as shown in the picture. If the arms are straight, the stub axles at the other end will line up perfectly. If they don't, one arm is bent. The stub axles should be perpendicular to the pivot shaft and it is fairly easy at this point to see which one is not in alignment.