Interesting bunch of views with respect to the origins of the 146.
My input is that when I was interviewed by HSA in 1966 for a test flying job at Dunsfold it was made clear to me by Harry Broadhurst that if they did not eventually get a contract to produce what became the Harrier I would have to go to Hatfield and do the 146. John Stamper took me through the design philosophy and said that it was intended as a hub and spoke aircraft to open up Africa. At the end of the spoke was just going to be a strip - not what we would recognise as an airfield – with negligible facilities. This meant that the aircraft had to have four small engines because they needed a three engine ferry capability to return to the hub to do the donk change. The high wing was to get the engines as far away from the FOD issues of strips as possible. Everything else stemmed from these two criteria.
In the event as we know HSA decided not to launch the aircraft. That was left to BAe many years later.