St James's Square Trust
Group From 1726
From the Picture source website: "... the St James’s Square Trust is intent on preserving tranquility and avoiding the incursion of large, disruptive commercial ventures in the Square. The gardens are not publicly funded, but depend on financial support from the building freeholders in the Square."
That website also has a History page which starts in March 1661 when the Earl of St. Albans acquired a freehold on St James’s Field and set about laying out the Square.