@Uxion: That was I was telling, simple arrows couldn't be able to pierce the plates. I remember that some of them even had the gaps (save those in the face) covered in chainmail for extra protection.
Now I'm remembering that war hammers were also created to pierce plate armor, but I don't remember if they were around in the 100 years war or not, but I think they did.
Those arrows were probably more aimed towards the horses than the armoured guys riding them. The mud, stakes and Englishmen with billhooks behind those stakes ought to do the rest. Either that or English longbowmen are armed with ye olde Medieval raillegonnes.