In 1968 I was 'keeper' of the RAF Coastal Command history room as one of my secondary duties whilst working 'down the hole'. As such I got to see a lot of documents as they were filed away or even just left out for perusal. Included were a lot of proposals for the Shackleton replacement, including all the ones mentioned above. However there were some even more esoteric designs, including one that particularly stuck in my mind - essentially a flying wing. This had all been sent up for storage since the Nimrod had been selected. Unfortunately this mine of historical information was on the top floor of HQCC - which was burnt down in early 1969. Not only was the document room destroyed, but also much of the other memorabilia as well.
I have never seen any mention of the flying wing design since, and no one else seems to have either - unless there is someone else out there in ppruneland?