Was he doing it before?
Wanking the cock of an invisible man?*
Is it an old gesture in Boris' body language repertoire or is it newly acquired from his role Trump model? Could Boris, actually, be wanking a tinny imaginary Trump?
Now on, this distinguished hand posture and movement will for ever be known as the Bo Gesture.
Once N1 at N10 Boris might well write to L'Académie Française in suggestion to change the spelling of beau to Bo!
More about the future N1 at N10 to be read at CW under, obviously, ...N1 here
Go on Bo Kill'em All!
( *Credit to the excellent John Niven)