LONDON, ENGLAND - JANUARY 30: Prince Charles, Prince of Wales and Camilla, Duchess of Cornwall prepare to travel on a Metropolitan underground train at Farringdon Station as they mark 150 years of ... more 

LONDON, ENGLAND - JANUARY 30: Prince Charles, Prince of Wales and Camilla, Duchess of Cornwall prepare to travel on a Metropolitan underground train at Farringdon Station as they mark 150 years of London Underground on January 30, 2013 in London, England. (Photo by Chris Jackson - WPA Pool/Getty Images) less