Ralph Richardson's love letters and diaries bought by British Library

Papers and correspondence from the actor Sir Ralph Richardson, including letters addressing his wife as "Ferret" or "Ferrety", have been bought for £120,000 by the British Library.

The acquisition will add to the British Library's archives of 20th-century acting knights, which already include collections belonging to Lord Olivier and Sir John Gielgud. The archive was bought from the Ralph and Meriel Richardson Foundation, a trust established by Lady Richardson to assist actors and actresses who have fallen on hard times.

Much of the collection is made up of Sir Ralph's letters, including those to his son Charles, and a set of love letters to Lady Richardson.

Correspondence with Sir Alec Guinness also features, as well as drafts of speeches, his sketchbooks, Christmas cards and even bank statements. There are two boxes of family and theatrical photographs, and even his flying logbook from his time as a pilot in the Fleet Air Arm, where he became known as "Pranger" Richardson for his lack of skill.

Other items in the archive include his passports and appointment diaries, pieces of wrapping paper he hand-painted for gifts to his wife, and the buttons from his military uniform. Sir Ralph, who died in 1983, successfully combined theatrical and cinematic roles. His final film, Greystoke: The Legend of Tarzan, was released posthumously in 1984 and earned him a second Academy Award nomination.

He was renowned for performances as Shakespeare's Falstaff and the archive includes his working editions of Henry IV with handwritten notes showing how he planned the delivery of his lines.

Kathryn Johnson, curator of modern drama collections at the British Library, said of the collection: "It is in beautiful condition, thanks in no small part to the meticulous care of Lady Richardson, who added dates and names to many of the photographs, and it is a pleasure to work on the papers.

"In combination with the Gielgud and Olivier papers, this acquisition offers a research treasure trove second to none."

One of the foundation's trustees, Brian Eagles of Richardsons' solicitors Howard Kennedy, said: "Sir Ralph wanted his archive to rest finally with a national institution. He would be delighted with his trustees' choice of the British Library, and that the archive is housed with those of his closest actor friends."

The British Library was assisted by a grant of £30,000 from the Friends of the National Libraries. Material from the archives of Richardson, Gielgud and Olivier are on display at the library until 25 May.