Again, we are trying to map the plants in a garden designed and planted by a master gardener with a lot of experience (and a big budget), but that person is gone and the records are faulty.

This is a big shrub, with a tree-like habit. Leaves are opposite, very hard and bearing sharp prickles. Most leaves seem mostly trifoliate, but there are some variations. There are no remains of flowers or fruits. Your help is much appreciated.