In a perfectly charming video about the Volkswagen ads in the 1960s, John O'Driscoll describes how the copywriter Bob Levinson set the tone of his writing.
"He put at the top of the copy: 'Dear Charlie' then wrote the copy as if he was talking to his best friend. And then he always put at the bottom: 'Yours sincerely and best, Bob.' And all he ever did was obliterate 'dear Charlie,' [and] take off the bottom bit. That's how they got the tone of voice."