Digby unsuccessfully sought an audience with James to try and explain himself, in Fraser's opinion suggesting either that the extent of his involvement was limited, or that he was "astonishingly naive and trusting of his sovereign's forgiveness." While imprisoned he busied himself with writing secret letters, smuggled from the Tower and not rediscovered until Kenelm Digby's death in 1665. Although he was fortunate not to suffer the fate of Guy Fawkes, who was tortured on several occasions, one of these letters hints that it had been "in a fashion, offered". He described his refusal to cooperate with his interrogators, boasted of his deceit, and how there was nothing he could do to make the plot appear less abhorrent to fellow Catholics. Digby also carved an inscription on the wall of his cell, extant as of 1996.
