Alan Rickman Was 'Frustrated' While Playing Snape in 'Harry Potter'

New details about Alan Rickman‘s career are coming to light after a box of his personal letters were put up for auction.

The late actor, who died of cancer in 2016, kept a letter from Harry Potter producer David Heyman and it’s included in the collection.

In the letter, Heyman thanked Rickman for his work on Harry Potter and the Chamber of Secrets, the second film in the franchise.

“Thank you for making HP2 a success. I know, at times, you are frustrated but please know that you are an integral part of the films. And you are brilliant,” Heyman said.

Rickman wrote a note titled “Inside Snape’s Head” while filming Harry Potter and the Half-Blood Prince. He said, “It is as if [director] David [Yates] has decided that this is not important in the scheme of things i.e. teen audience appeal.”

The collection of memorabilia is worth more than $1.2 million, according to The Independent.