The A7 submarine sank at Portsmouth with all souls lost in January 1914. It has remained on the seabed, largely unexplored, until a project, in 2014, to fully map and record the wreck. This report covers the aims, results and conclusions of that project.Its detailed record of the submarine is highly significant as the A7 is the most complete example of an A class submarine in existence. As a result, it greatly enhances our knowledge and understanding of this pioneering British submarine class, which was both the forerunner of British WW1 submarine warfare, and the foundation of post-war developments. The long-debated cause of its destruction was also finally determined by the project. The report also provides a concise history of early British submarinewarfare and technology. Finally, it records the lives of those who went down with the submarine, and details the many risks and challenges faced by those brave enough to man these early submarines.