What?

Lancelot Capability Brown is well documented during his lifetime through the two-dimensional image.

This iconic painting in the National Portrait Gallery collection will be one of the important documents yielding visual information for the creation of a sculpture head of Brown:

after Nathaniel Dance (later Sir Nathaniel Holland, Bt)
oil on canvas
circa 1770
NPG 1490
© National Portrait Gallery, London

Several people have suggested ‘Why not a full size figure?’ and my reply would be that most public sculpture today is both prescriptive and descriptive – arms and legs dressed in the contemporary garb of the day, when all the importance is in the head – the source of thinking. It also enables the sculptor to use resources to reconstruct with visual acuity, rather than just a generic result.