This statue is in the centre of St James’ Square, SW1, London.
William III is William of Orange. He was King of England, Scotland and Ireland from 1688 to 1702. The statue was originally proposed in 1687. It was completed in 1807, which is the date on the plinth. There were a number of delays. The first commissioned sculptor, John Bacon Senior, died. The sculpture was eventually created by his son John Bacon junior.
As you see, the statue has green highlights. This is how it was. It is bronze, which is an alloy of copper and tin: tin 12% roughly. The green is verdigris: a mixture of copper compounds. Wikipedia is lyrical on the subject:
“Verdigris is a variable chemical mixture of compounds, complexes and water. The primary components are copper salts of acetate, carbonate, chloride, formate, hydroxide, and sulphate…..All the components are in an ever-changing and complex reaction equilibrium that is dependent on the ambient environment.”Wikipedia entry for verdigris
This makes it sound like a 21st century environmental art project.
Written on the plinth is: GVLIELMUS. III. And on the other side:
The sketch took about half an hour. Colours are mostly Phthalo Green, Prussian Blue, and Perinone orange. In Jackson Watercolour sketchbook.