Young Welshman Gareth Williams was a child prodigy who became a talented mathematician and codebreaker working for GCHQ, MI6 and the intelligence services but in the summer of 2010 he was found dead in a bag in the bath at his apartment in London. In this first episode Sian Williams looks at what we know about Gareth and reminds listeners of the bizarre nature and circumstances of his death.

Death of a Codebreaker is presented by Dr Sian Williams with contributions by Dyfan Rees and Tracy Cardwell.