I'm not an expert on Australian copyright law, but I think the answer would be yes - provided that the 1937 distribution of the film constituted publication (legally) of the music score by Churchill. For laws rooted in the English common law tradition (Australia, NZ, Canada and the USA), publication is a very important aspect in determining the start of a copyright term. For example, if Churchill (who died more than 50 years ago) composed the score in 1937 but the film's distribution did not constitute publication, which took place legally only when Walt Disney Music issued a simplified piano arrangement in 1987, the Canadian term of copyright would start counting down in 1987, the work entering public domain only after 50 years (in 2038). Under the ancient common law, unpublished works were under perpetual copyright, which was divested only upon publication. In the USA, this all changed in 2003, when all unpublished works of authors dead more than 70 years entered the public domain. Ironically, as of Jan. 1, 2013, all unpublished work of Churchill will enter the USA public domain. Certain works of his could be protected longer in Australia or Canada, if they were only published last year for the first time.