Thanks for reviving this vintage thread.
An image of a youngish and thin Robert Churchill explains a lot. He did become rotund later in life - see the cover of the his 1955 "Game Shooting". Note the left hand is fully extended and at least from this angle the gun appears to have a long LOP



Nice discussion of the Stanbury and Churchill methods here, by Michael Yardley
http://www.positiveshooting.com/WingShooting.html