kogan

Certainly - the norway maple is just too big for the garden, and I am intending to plant two holm oaks on either side which I will keep in semi topiarised form instead. However, where it remains is useful for a bit of screening, and therefore I plan to leave the trunk as is for now and grow ivy up it

Yes it is, thanks for correcting me! Does it have an effect on girdling success?

Those trees with obvious rings across their trunk

I understand those trees which are not particularly ring-like (like an Oak) are less effective to kill in this way but will it still work eventually? Thanks!