"I hope to remain one of your 'sacred cows'."

Grace Kelly became Princess of Monaco when she married Prince Rainier in 1956. Six years later, Alfred Hitchcock offered the retired actress the leading role in his new film "Marnie" (1964). Grace was eager to work with Hitch again, but the people of Monaco were not too thrilled with the idea of the princess playing a kleptomaniac. Due to the protests in her new country, Grace withdrew from the project, leaving Hitchcock to look for a new leading actress (whom he would find in Tippi Hedren).

Here is a letter written by Grace Kelly to Alfred Hitchcock, in which she expresses her regret over her withdrawal from the project. And the second letter is a draft copy of the letter Hitch sent to Grace.

Source: hitchcock wiki

Transcript: 

June 18th, 1962

Dear Hitch- 

It was heartbreaking for me to have to leave the picture- I was so excited about doing it and particularly about working with you again-

When we meet I would like to explain to you myself all of the reasons which is difficult to do by letter or through a third party. It is unfortunate that it had to happen this way and I am deeply sorry- Thank you, dear Hitch, for being so understanding and helpful- I hate disappointing you- I also hate the fact that there are probably many other "cattle" who could play the part equally as well- Despite that I hope to remain one of your "sacred cows"-

with deep affection- Grace

Source: hitchcock wiki

Transcript: 

Draft

June 26, 1962

Dear Grace,

Yes, it was sad, wasn't it. I was looking forward so much to the fun and pleasure of our doing a picture again.

Without a doubt, I think you made, not only the best decision, but the only decision, to put the project aside at this time.

After all, it was only a movie. Alma joins me in sending our most fondest and affectionate thoughts for you.

P.S. I have enclosed a small tape recording which I have made especially for Rainier. Please ask him to play it privately. It is not for all ears.

Note: Alma whom Hitch mentions in his letter, was his wife Alma Reville. They got married in 1926 and remained married until Hitch's death in 1980.