...what else?...the 'sweep' program in 'd'....go figure:

https://en.wikipedia.org/wiki/Qin_Dechun#/media/File:Qin_Dechun.PNG

"the masonic chessboard" replies MI5 ONLINE...exactly that...see previous notes upon the 'sooty and sweep' line...along with marr angling for 'something' around chequers....and the chequered etc etc...mark r had used the following image to represent himself: