I have an idea you might use. I give it to you freely and without any intention to use it myself.
It is this. I have been rereading the Saxon Stories and thinking about defences that can be made at short notice. I had the idea of willow withies strung on a hawser or sturdy rope and tied off at either end. they are very resilient and would withstand a sword strike or an axe strike because they would give and absorb the force. In addition the attacker would be vulnerable to a spear or arrow while trying to cut the rope.
Obviously this has limited use but it has the benefit of being easily and quickly made and would augment a shield wall.
The Japanese used similar defences which were used against katana and naginata.
Lastly please let me tell you that your books are great. Uhtred is a brilliantly flawed character, fully the equal of Sharpe.
Kind regards,
Danny Martin