Cornelius Ryan was an Irish journalist and author born in Dublin in 1920. He wrote his most famous work, 'The Longest Day: 6 June 1944 - an account of the D-Day invasion' in 1959. As a war correspondent for the United Kingdom’s broadsheet newspaper the Daily Telegraph, Ryan travelled with various United States Army Air Force units before joining General Patton’s Third Army in France and Germany, reporting on events until the end of the war in Europe.

After the war, Ryan returned to Normandy, and it was this visit that inspired him to write the story of the D-Day campaign from both Allied and German perspectives. As part of his extensive research, Ryan conducted more than 1,000 interviews with Allied and German soldiers, sailors and airmen, many of them of senior rank. The Longest Day is based on those interviews. The continued interest of people across the world in Operation Overlord ensured that the book was a huge success, so much so that it was made into a blockbuster Hollywood film of the same name, which was released in 1962.

Ryan helped in the script-writing process and the film, featuring major stars such as John Wayne and Richard Burton, received significant praise from critics and audiences worldwide, winning two Oscars at the 1963 Academy Awards. The D-Day Archive has copies of 36 of the interviews Ryan undertook with the Allied and German service personnel. The documents are accessible to view on request in the Portsmouth History Centre.