SYDNEY, AUSTRALIA - APRIL 20:  Prince William, Duke of Cambridge (L) and Catherine, Duchess of Cambridge (C) sign the First Fleet Bible and Prayer Book following Easter Sunday Service at St Andrews Cathedral on April 20, 2014 in Sydney, Australia. The Duke and Duchess of Cambridge are on a three-week tour of Australia and New Zealand, the first official trip overseas with their son, Prince George of Cambridge.  (Photo by Lisa Maree Williams - Pool/Getty Images)