"Immigrant Song" was written about the Viking invasions of England and inspired by a short tour of Iceland in June 1970. It was released as a single in the US and became a top 20 hit. It was the opening song for the band's appearance at the Bath Festival of Blues and Progressive Music and at subsequent gigs for the next two years. It was popularised in the 2003 movie "School of Rock", after Jack Black made a short video with fans asking for permission for its use. Page clarified that the song's opening is a combination of a voice and echo feedback.