In August 2010 the death of a brilliant young mathematician in extremely bizarre circumstances sent shockwaves around the world.

The badly decomposed body of Gareth Williams, 31, was discovered by police locked inside an airtight holdall in the bath of his central London flat.

The revelation that Mr Williams was a secret agent working for MI6 catapulted the story on to the front pages and spawned countless conspiracy theories as to how he might have died. Speculation ranged from a state-sponsored assassination to a sex game gone wrong.

But despite a coroner’s inquest and two lengthy police investigations, his grieving family and the wider world remain no closer to understanding exactly what happened to Mr Williams.

Now, almost a decade on from his untimely death, the Telegraph has re-examined the leading theories and spoken to a number of expert sources in order to assess whether the truth will ever be revealed.

The victim

Gareth Williams was born and brought up in a small Welsh-speaking community in Anglesey, North Wales.

A child prodigy he took his maths GCSE while still at primary school, completed his A-level by the age of 13 and graduated from Bangor University at 17.

While conducting postgraduate research at Cambridge University he was approached by scouts from GCHQ and offered a role working as an analyst at its secretive Cheltenham headquarters.