On this day in 1979 – Blondie scored their first No.1 album when their third studio album Parallel Lines started a four-week run at the top of the charts. The album featured the singles ‘Heart Of Glass’, (their first No.1 hit on the American Billboard Hot 100), ‘Hanging On The Telephone’ and ‘Sunday Girl.’ Parallel Lines took its name from an unused track written by Harry and became the UK’s biggest-selling album of the year.