From codes that everyone else thought were uncrackable to the apparent nonsense of quantum mechanics, only a heretic could brave the derision of their peers and start a scientific revolution. 'Heresy is part and parcel of science,' argues Simon Singh in this witty and insightful talk at the Cheltenham Science Festival. But while all great truths begin as heresies, not all heresies become great truths, cautions Singh – as he introduces his very own mathematical formula 'proving' the Teletubbies are evil