Pi love you! Hand-written maths lessons that Dambusters 'bouncing bomb' inventor Barnes Wallis used to woo his 17-year-old wife who was HALF his age are set to sell for £2,000 The celebrated World War Two hero fell in love with his much younger cousin Molly Bloxham in the 1920s Her father felt it was inappropriate for her senior suitor, almost 20 years older, to be writing to the teenager But he did allow her to correspond provided he taught her mathematics, which she was studying at college Some 250 letters covering calculus, trigonometry and electrostatic induction were written over 16 months Now the archive of Wallis' increasingly romantic notes is set to go under the hammer at auction tomorrow