Q.Can I Reverse Copice To Get A Tall Standing Tree
I have a number of previously copiced clumps which I wish to encourage to become tall standing trees. Can I cut away all smaller growth leaving one or two of the biggest and will those remaining grow into a full tree? The tallest trunks are currently about 20ft tall. They may be Hazel.

Certified GKH Gardening Expert
Yes. They often grow to about 30 feet tall. This article should help:
https://www.gardeningknowhow.com/ornamental/shrubs/shgen/pruning-a-shrub-into-a-tree.htm