How to remove Blackthorn creeping roots from garden?

Question

The roots appear to have suckers growing at different intervals along the main root.

Answer 1

Unfortunately, when there are tree root problems, the best answer is to remove the tree.

https://www.gardeningknowhow.com/ornamental/trees/tgen/problem-tree-roots.htm

https://www.gardeningknowhow.com/ornamental/trees/tgen/shaving-down-tree-roots.htm