The issue of patent rights was a complex one, and attempts to negotiate deals between Britain and the United States in 1942, and between Britain and Canada in 1943, had failed. After the Quebec Agreement was signed, British and American experts sat down together again and hammered out an agreement, which was endorsed by the Combined Policy Committee in September 1944. This agreement, which also covered Canada, was retrospective to the signing of the Quebec Agreement in August 1943, but owing to necessary secrecy, was not finalised until 1956, and covered all patents held in November 1955. Each of the three countries agreed to transfer to the others any rights it held in the others' countries, and waive any claims for compensation against them.