FORTUNE — She wasn’t well known outside Apple AAPL , but to reporters who covered the company closely — especially if they got anywhere near Steve Jobs — Katie Cotton carried a lot of weight. Fortune in 2010 named her one of the 50 Most Powerful Women in business.

Much has been written about Katie since Wednesday, when re/code’s John Paczkowski reported that after 18 years with Apple, she was leaving the company.

What did she bring to the party? Here’s John Gruber’s take:

Most big corporations employ outside PR agencies. Not Apple. Apple’s internal public relations team is itself a world-class agency. That team was built entirely under Cotton’s leadership.

Cotton was never pictured on Apple’s executive leadership page, but my impression has long been that she was among the very handful of most influential executives at the company. It is difficult to find a photograph of Steve Jobs or Tim Cook at a press event in which she is not at their side. Paczkowski put it well: Katie Cotton “played a key role in shaping the mystique and exclusivity surrounding the Apple brand.” — From Daring Fireball