Ah yes, the article I read (Classic Bike September 1991) was about the AJW 'Grey Fox', a rather unique bike with a JAP side-valve parallel twin, Dowty Oleomatic forks and (seemingly) no silencers.
However the AJW 'Rain gutter' is different to the 'v' on your tank ... the AJW's 'v' faces the other way and shepherds the water into some sort of central down-pipe. Whatsmore I gather the rain gutter is a detachable unit.
So sorry to lead you on, but the triangle on the tank rang bells.
to look at i'd say your tank looks francis-barnett'esque, but i dont know enough about pre-war bikes to be sure