Young Welshman Gareth Williams was found naked inside a relatively small bag in his bath in 2010. And another theory is that he was the victim of a bizarre sex game gone wrong. There are suggestions he may have had an interest in Claustrophilia - pleasure derived from being in a confined space. But how much evidence is there? Here Dr Sian Williams looks at what we know and don't know about Gareth's private life.

Death of a Codebreaker is presented by Dr Sian Williams with contributions in Episode 5 from James Pepper, Ashley Byrne, Tracy Cardwell and Wayne Wright.