Supermarine Walrus - Wikipedia, the free encyclopedia

One of its more unusual characteristics was that the control column was not a fixed fitting in the usual way, but could be unplugged from a socket at floor level, there being two sockets. It became a habit for only one column to be in use and when control was passed from the pilot to co-pilot or vice-versa for the control column to be unplugged and handed over.

Obviously the notion of redundancy had yet to occur to anyone….