The cheery chappie boisterously farting in the face of the Georgian monarch is an early incarnation of John Bull. Not the neat fellow in the Union Jack weskit with bulldog, but the original, roistering symbol of the ordinary man who can detect the smell of corruption-heavy bullshittery by the powers that be and joyously farts in the face of the Establishment. Bit like us, really. I stumbled across this on Youtube:
All together now, one, two, three - FART.