Adams was on one of the U.S. talk shows, maybe Johnny Carson or Dick Cavett (we're going back a ways, here) and told a story on himself. He said he decided to use it in a book because after he told it a few times he saw someone else trying to lay claim to it.

He was in a coffee shop waiting for his train, and bought his coffee and a package of cookies and a newspaper. Because of the crowded time of day, he ended up sharing his table with a stranger, who sat down opposite him. They didn't speak. When he looked up from his paper, Adams was shocked to see the man opposite him reach out, rip open the cookies, and eat one. Adams thought he'd shame the fellow into leaving his cookies alone, so he reached out and picked up one and ate it. They ended up going back and forth with the cookies, Adams getting more irritated with each round. A train was entering the station, the stranger got up and left, never having said a word. Only then did Adams pick up the rest of his paper and spotted his own unopened package of cookies on the table. He figured this guy had a similar story to his. :)