Rudder shaft keyway issue
On purchasing Peter Robyn people explained the tiller "slack" was most likely a worn key. With the boat on the slip for the engine install I took the opportunity to have a look. Sadly, it was not the key but the keyway in the 1400mm brass rudder shaft. The stainless key of course is stronger than the brass so the shaft keyway was the part that suffered the wear.
While removing the shaft I also broke the bottom of the shaft as the whole thing seemed to have suffered electrolysis reaction between the stainless and brass parts. Fortunately by this time I had discovered a new shaft would be necessary anyway.
A new shaft has been made from 316 stainless. Much stronger and should avoid this problem in the future.