Time travel, wormholes, a lost security pass and a nice cup of tea. These are the elements that constitute Steve Punt’s Theory of Grand Unified Comedy as he presents 'Big Bang Day, The Genuine Particle' whirling into existence on BBC Radio 4. Starring Reece Shearsmith and Geoffrey Whitehead, it’s a comedy thriller set underground in the Large Hadron Collider and bears the unique property that every bit of physics in it is true - theoretically at least.