National Security, or in these cases perhaps the misuse of Information and the intentional suppression of information, trumps 5 dead Unfortunates in the slums. So why does everyone think of Jack the Ripper as the story during the Fall of 1888? The only reason is because we only have information as relates to the domestic police investigations into the crimes. How could we know if National Security investigations into the Ripper crimes led to Irish self rule terrorism, or vice versa?
One wonders what other agencies found out while conducting their own investigations.
I think Simon hints that Tumblety was a relevant character that Fall, just not relevant to investigations into the killings of the Unfortunates.