That's very helpful, thank you Kevin - In my story I want them to look very imposing - presumably they would have been intimidating to horses etc.

Do you know anything of the Signal Redoubt at the battle of Nivelle - it is a curious name, why was it called that? Do you know what it would have looked like? There is much talk of it being a great fort / obstacle etc.

Also, I looked at Guy de Vernon. I don't think there are any illustrations in there and unfortunately I do not read French very well! But all I need to know is that there were lots of nasty wooden spikes....

Thank you ever so much for your help, I really appreciate it.