Frank Close is a theoretical particle physicist and a pioneer of popular writing about physics. His first book aimed at a non-specialist audience, The Cosmic Onion, was published 35 years ago. His latest, Half Life, is the story of physicist and spy, Bruno Pontecorvo. Frank has also had a distinguished research career studying the fundamental structure of matter. It was during his PhD in the late 60s that quarks were discovered. These are the fundamental entities we now know make up particles such as protons and neutrons, which in turn make up the nuclei of atoms, and therefore all of us and everything around us. Frank Close went on to make a name for himself studying what holds the quarks together inside matter. Among his many best-selling books was his thorough account of the controversial claims about the discovery of cold fusion - the idea of unlimited fusion energy in a test tube - and which brought the remarkable story to the world's attention in his book Too Hot to Handle. Frank has spent most of his working life around the Thames Valley - at the Rutherford Appleton Labs, and now at the University of Oxford where is an emeritus professor of physics. In front of an audience at the Cheltenham Science Festival Jim al-Khalili discusses physics and writing with Frank Close.