As the host of BBC Breakfast and anchor of Channel 5 News, Sian Williams appeared unflappable. She delivered news of devastating events to the nation, from the 1989 Hillsborough disaster to the aftermath of Princess Diana ’s death in 1997 and the Kashmir earthquake in 2005. What viewers didn’t know was that Sian, 61, suffers with crippling anxiety that, at times, she worried might derail her sparkling career. She says: “I was once so overwhelmed with anxiety that I backed into my programme