Guest Ray wrote: 'My understanding is that the “two fingered salute” was used by English archers at the battle of Agincourt to demonstrate to the French that they still had their bow stretching fingers left (the enemy used to chop the fingers off if they were captured to prevent them firing a bow.)'

Historically, there is no evidence for this. See Agincourt myth and the Snopes version
of the story Snopes - finger removal.

Coincidentally, while undertaking completely unrelated research, I found the first film recording of the British 'V' sign (not the polite Churchill version).

Rotherham, Yorkshire, 1901