Simpson was a battlefield tourist and a great admirer of Wellington and his Army. Soon after the great battle, he visited the field and describes what he saw, as well as making a collection of the reminiscences of the battle by "many of its gallant soldiers". Of great value, as his collected notes were written so soon after the battle "that the marks of artillery wheels are still visible", and the spoils of war were being offered for sale by the local "peasants".
Collecting soldiers' reminiscences before the myth-making got under way, Simpson's observations are an important source for the aficionado of the Battle of Waterloo.