At the entrance to a big office in London there was a book which all employees had to sign when they arrived each morning. At nine o’ clock, the manager’s secretary, who lived in a small flat above the office, had to draw a red line under the last name in the book, and anyone who came after that had to explain why he was late.
Whenever there was a thick fog in the city, the first person who arrived late usually wrote: “Delayed by fog” under the red line in the book, and then everybody else who came after that just put, “ditto” underneath.
But one foggy morning, the first man who arrived late wrote: “My wife had a baby early this morning” instead of “Delayed by fog” under the red line in the book. Twenty or thirty people who came after him put, “ditto” underneath this as usual.