Paul, I was hoping someone would pitch in with its technical name or rather the name for that configuration of components. Iv looked in a few vehicle dynamics textbooks that give detailed definitions of lots of suspension setups and the various relationships required to find the constants needed when analysing different setups. But non I have cover the arrangement used by Morgan.
It's known as sliding pillar Leon, but technically it is more of a sliding collar, because the pillar (the king pin) is fixed and the collar with the stub axle attached does the sliding.
