"The Funeral Procession of Arthur, Duke of Wellington" is a hand-coloured etching more than 20 meters (67 feet) long. It has rarely been exhibited, and never before displayed in full online.
In conjunction with the exhibition "Wellington: Triumphs, Politics and Passions" (March 12 to June 7 2015) the National Portrait Gallery has produced this app allowing you to view the entire work in detail on your iPad.