You wouldn't happen to remember what type of arrow heads they were using in their test to do you? If I remember correctly the English had poor luck in penetrating armor until they switched to what is called a Bodkin arrow head. It's a very narrow very pointed arrow head that is just big enough to allow the shaft to pass through the hole it makes. Once they switched to those the arrows would zip right through plate armor.
Found some stuff HERE
(the second link has a picture of different types of arrow heads)