Article: Sex was used as an important element in the content and marketing the paper from the start, which Lamb believed was the most important part of his readers' lives. The first topless Page 3 model appeared on 17 November 1970, German-born Stephanie Rahn; she was tagged as a "Birthday Suit Girl" to mark the first anniversary of the relaunched Sun. A topless Page 3 model gradually became a regular fixture, and with increasingly risqué poses. Both feminists and many cultural conservatives saw the pictures as pornographic and misogynistic. Lamb expressed some regret at introducing the feature, although denied it was sexist. A Conservative council in Sowerby Bridge, Yorkshire, was the first to ban the paper from its public library, shortly after Page 3 began, because of its excessive sexual content. This decision was reversed after a sustained campaign by the newspaper itself lasting 16 months, and the election of a Labour-led council in 1971.

Question: When was the library ban reversed?
1971