The transcript of his interrogation by Special Branch, which was withheld at his trial at the Old Bailey for high treason, confirms the belief that the 56-year-old convert to the cause of Irish nationalism threw away whatever defence he might have had by not allowing defence counsel to call evidence in support of a presumed peace mission.
As it was, the rising went ahead with a bloody contest for the Dublin General Post Office which left 450 rebels, soldiers and civilians dead.
The papers, from the Public Records Office in Kew, west London, show the lengths to which the British government was prepared to go in suppressing this interpretation of Casement's mission, which, poignantly, was regarded in further evidence as a madcap venture by US Irish republicans and its German sponsors.
It ended humiliatingly, on the beach at Tralee, after Casement, a retired civil servant, had paddled ashore in a canvas boat from a U-boat that had brought him and two companions - one who turned King's evidence against him - from Wilhelmshaven. Two policemen took him away at rifle-point and he was handed over to Special Branch, which had been tracking his movements since he left Ireland before the First World War for New York, and then Germany, where he tried to raise an Irish brigade from Irish prisoners of war - the basis for the charge of treason under a 1351 Act.
Interrogated at Scotland Yard by Special Branch and Captain "Blinker" Hall, the celebrated naval intelligence specialist, he refused to admit charges that he had been paid by the Germans to sail to Ireland with his brigade and lead the rising. He said: "The proposal came upon me as a thunderclap. I said [to the Germans] I have been here for a year and a half and begged you again and again to send rifles to Ireland and you refuse always. Now you spring it at my head at the 11th hour, when I have long given it up, of hoping to arm my countrymen. At last you have come up with this offer of belated help and it synchronises with what I can only regard as a hopeless uprising in Ireland where my countrymen will be shot down. Obviously I think it is cowardly, dastardly and I go alone.
"They wanted me to take all my Irish boys. Those young men ..." The interrogator said "50?" Casement answered: "More than 50. We had a terrible fight [with the Germans] and I won the day. I said I won't do it. I shall not have it said I handed these men over to the hangman."
The Germans insisted instead that an arms ship, the Aud, should carry 20,000 rifles and a few machine guns for the rising, which Casement, among others, saw only as a last resort at some future date. She was scuttled when intercepted by a British patrol boat.
Casement said he thought the Germans planned to stage a Zeppelin attack in support of the rising but said he knew nothing of a second arms shipment that would only have been sent if he gave a signal.
Just before Casement's execution on 3 August 1916, the Attorney General, FE Smith, later Lord Birkenhead, and a former political opponent in Ireland, wrote a minute agreeing with Home Office plans to feed the press stories undermining the "abort mission" story.
The Home Office "thought it possible to get two papers, the Morning Post and the Daily Chronicle, to write stories pointing out that the Aud was in close attendance to Casement" and that when he landed he brought a large Irish flag with him.Reuse content