Leicester University raised pounds 80,000 to secure the papers, which include typescripts, notes and unpublished works from the controversial author of Entertaining Mr Sloane, Loot, and What the Butler Saw.
It launched its appeal on 14 February, to secure, house and conserve the papers, which were being held by Orton's family. The university was given a deadline of 30 June, after which the papers would have gone on the open market, and possibly left the country.
Leicester University librarian Dr Timothy Hobbs said yesterday that the purchase had been "a tremendous achievement and a triumph for those who wish to preserve our great literary heritage.
"These papers will now be retained in Joe Orton's birthplace and will provide enormous benefits for students, scholars and people interested in learning more about the playwright," he added.
The papers, he added, offered "fascinating insights" into the mind of a "very anti-establishment figure".Reuse content