Roger Casement, the retired British consular official tried for treason and executed for securing German rifles to help the 1916 Rising in Ireland, has been a focus of controversy since the 1930s, with specific reference to the so-called Black diaries allegedly forged by British intelligence in c.1916. Forensic tests on the diaries commissioned by a committee chaired by W.J. McCormack have now shown that the diaries were written by Casement. This work is centred on W.J. Maloney, whose 1936 book, “The Forged Casement Diaries”, brought the topic to the attention of the Irish public, and was part of an Irish-American campaign to influence the domestic politics of the Irish Free State. The book raises questions about intelligence work, archival engineering, IRA unofficial action, Nazi propaganda and new light is shed on major figures such as Eamon de Valera and W.B. Yeats, as well as on a cast of colourful bit players.