Ahhh...the Pembroke. RAF Eastleigh [Kenya] owned one in the late 1950s as Station Hack .It eventually went to Germany, and then was sold in the UK, but ended up in the US I think.
I was offered a seat in it often, even though I realised it was simply to have someone to turn the props through a full cycle [nine blades?], before start up. It was a peculiarity of the nine -cylinder Alvis Leonides engines I suspect, something to do with oily stuff. In the Twin Pioneers they carried a pole with a loop on it to do the same job!