This fonds includes seven letters of Anders Naessil: five from Arthur Koestler to A. Naessil, one from A. Naessil to Newsweek magazine, and one from Marie Whiteside, Editor of Newsweek to A. Naessil.
- Letter from Koestler to Naessil replying to a previous letter, mentioning Naessil's book on Hemingway, Sartre, and a Nobel banquet that Koestler attended. Dated 21 June 1980.
- Letter from Koestler to Naessil thanking him for his offer of hospitality, but declining due to ill health. He also mentions the book he was working on at the time, Bricks to Babel - Selected Writings with Comments by the Author. Dated 24 July 1980.
- Letter from Koestler to Naessil thanking for the copy of a letter Naessil sent to the French newspaper Le Monde. Dated 30 September 1981.
- Letter from Koestler to Naessil discussing the extract from the 'Hemingway book' Naessil sent him, and the best way to get it published. Dated 10 February 1982.
- Short letter from Koestler's secretary Cynthia Jefferies to Naessil, thanking him for his letter and explaining that Koestler can only see close friends due to ill health, and asking him to 'send on the clippings and drink the wine to his health'. Dated 18 October 1982.
- Typed letter sent by Naessil to the newspaper Newsweek, criticising an obituary that was published shortly after Koestler's death. Dated March 1983.
- Reply to the above letter from Marie Whiteside for the Editors of Newsweek, to Naessil. Dated 21 June 1983.