SIR TERRY PRATCHETT is the acclaimed creator of the bestselling Discworld series. He was appointed OBE and a Knight Bachelor in recognition of his services to literature. He died in 2015.

SIR TERRY PRATCHETT is the acclaimed creator of the bestselling Discworld series. He was appointed OBE and a Knight Bachelor in recognition of his services to literature. He died in 2015.

IAN STEWART is a Fellow of the Royal Society, a professor of mathematics at the University of Warwick, and the author of numerous books on math and popular science, as well as science fiction novels co-authored with Jack Cohen. JACK COHEN is a professor of biology and an honorary professor of mathematics at the University of Warwick, and has co-authored several books with Ian Stewart.