“There isn’t a hint, and it isn’t dated.”
“When was it written?”
“Some time during the week before his death.”
“How can you prove that?”
“Well, it’s rather funny. The copying-ink we used to use in the office was a sticky purple kind of stuff. But we changed to Stephen’s blue-black copying-ink for some reason or other a week before he died, and this letter was written in the new ink.”
“Did Sir John open his own letters at the office?”
“No, the confidential clerk opened everything addressed to anybody. It was the understood thing amongst the lot of us that everything that arrived at that address must be the common interest and knowledge of the firm, so nobody used the address for his private purposes.”
“But suppose a letter marked ‘Private,’ and addressed to one of you personally arri
