In the novel Postern of Fate, Colonel Atkinson is a contact of Tommy Beresford from the old days when they worked on behalf of British intelligence.
Atkinson was pleasantly surprised to learn that Tommy and Tuppence had moved to Hollowquay and into a house named The Laurels. He seemed to believe that Tommy and Tuppence must still be working for the secret service because of this. Atkinson told Tommy that "a great deal was never found out about all that business." When Tommy asked him to elaborate, Atkinson mentioned "the Cardington Scandal" which came out after the "what-you-call-'em letters" and the "Emlyn Johnson submarine business".
According to Atkinson, the letters, if they had come to light would have embarassed some highly trusted people in the government. He believed that security people searched the hosue because they believed there was valuable evidence to be found but didn't find anything. In fact, Atkinson thought if the papers should come to light, there were still some people who would not be pleased. Ominously, he warned that these people could be dangerous or are in contact with those who are dangerous. He concluded by urging Tommy to be careful and to look after Tuppence.