“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 arrived. What would happen?”
“Oh, Smith would open it!”
“Has Smith seen this copy?”
“Yes, and he says no letters arrived at the office for Sir John, within the last month of his life, that this could possibly have related to.”
“Then Sir John must have received it at his own address?”