Seven people have been charged in relation to the operation, including former News International chief executive Rebekah Brooks, Sun chief reporter John Kay and Ministry of Defence employee Bettina Jordan-Barber.
Besides the letters (to a range of correspondents stretching from John Lennon and John Updike to Rajiv Gandhi and the socks department at Brooks Brothers), there are memorandums (many to the four Presidents he served, Lyndon Johnson and Gerald Ford being the others), notes to himself summarizing conversations he considered important, and entries from his private journal, which include some delightful travel writing.