How many times must it rain before you never ever leave house without an umbrella? If you're like me, this question should make you frown. For most people, whether or not to take an umbrella is a day-by-day decision, based on the weather, the sky and season.

However, since 23 December 2001, I have had to remove my shoes every time before entering an aircraft anywhere in the world. All it took was a single attempt by a one person to detonate an explosive device hidden in his shoe. Richard Colvin Reid, a Britisher, boarded American Airlines Flight 63 between Paris and Miami, with explosives packed into his footwear. He failed to detonate them and was sentenced to 110 years in prison - but boy, did he change aviation security forever.