Details from an extraordinary exchange of letters between a care worker from Nottingham, in England's East Midlands, and the alleged architect of the 9/11 attacks were revealed Saturday, offering an unprecedented insight into the mind of one the world's most notorious Islamic militants.

Khalid Sheikh Mohammed, 49, who is being held at Guantanamo Bay, Cuba, has endured the harshest of the CIA's interrogation methods and allegedly confessed to a career of atrocities.

Pre-trial hearings before a military commission are due to be held at Guantanamo next month. In his letter to Rory Green, 25, Mohammed wrote: "I appreciate your deep concern regarding my worldly and hereafter life. . . . You asked me to repent from my sins. For your own information, I never stop." Green began the correspondence when he was studying for a degree in athletics at Wingate University in North Carolina in 2011 after reading a newspaper article about Mohammed. A devout Christian, Green wrote: "I am not here to trick you, [or] make you feel worse than anybody in the world. There is hope in forgiveness through Jesus Christ."