Complex sentence: Newlyn has a plaque to this effect on the side of a building on its quay, erected in remembrance of Plymouth historian Bill Best Harris, whose research is believed to have uncovered this little-known detail about the voyage.
Split into simpler sentences: Newlyn has a plaque to this effect on the side of a building on its quay. It was erected in remembrance of Plymouth historian Bill Best Harris, whose research is believed to have uncovered this little-known detail about the voyage.