In reply to Mooncat: Finances aside, I would expect the "Faceless Herberts" to treat getting to the bottom of this as a priority.
When the russian dissident Alexander Litvinenko was murdered by Polonium poisoning the investigation uncovered everything down to the seat on the plane on which the poisoner came into the country.
When Georgi Markov was poisoned with a microscopic ricin filled pellet fired from an umberella "air gun" they even knew who the assasin was.
These 2 unfortunates weren't even one of "ours".
You cannot , surely, think that there is not something suspicious about the fact that the security organisations don't seem to know what went on??
I would have expected at least a plausible "cover up " story