Detectives investigating the mysterious death of an MI6 agent reportedly misidentified a Welsh mountain as a secret code. The decomposing body of Gareth Williams, a 31-year-old mathematics prodigy, was found padlocked inside a red North Face bag in his Pimlico flat in August 2010, triggering a significant investigation that granted Scotland Yard unprecedented access to intelligence services.

During the inquiry, officers found a jumbled phrase in Mr. Williams’ diary that they believed to be an unbreakable cipher holding potential clues about the events preceding his demise. However, the note was later revealed by his friends to simply be the name “Cadair Idris,” a Welsh mountain, written in his native Welsh, indicating that Mr. Williams was preparing for the Snowdon marathon.

The investigation faced criticism for several “embarrassing failures,” with the police being labeled as inefficient. Despite findings suggesting Mr. Williams died alone after locking himself inside the bag, doubts persist regarding this theory. A specialized forensic review in 2021, closed in 2024, failed to disprove the initial theory. Expert Peter Faulding dismissed the possibility of a solo death, emphasizing the lack of physical evidence supporting such a scenario.

The Metropolitan Police stated that while the case is not being reopened, any new evidence concerning Gareth Williams’ death will be reviewed by specialized detectives. The force expressed condolences to Mr. Williams’ family and reiterated its commitment to investigating any new information related to unexplained deaths.