What surprised me as I got into writing the book was the wealth of unpublished material that was available. This has helped to tell a slightly different story of some of the better known events, primarily the sieges. More importantly, it has allowed me be to build a better picture of the true role of an Engineer Officer in the Peninsular War.
The amount of material available also meant that some hard decisions had to be made. Several events that played their part in winning the war were almost completely disconnected operationally. So the extensive defensive work done by the Royal Engineers at Cadiz and Gibraltar has not been covered. Neither has the East Coast campaigns of 1812-3. Along with the American campaign of 1814-5 and the Waterloo campaign there is another book required to complete the story of military engineering in the Napoleonic Wars.