Songfacts®:

• This song started as a lyric Tom wrote when he was still living in Brighton on the South Coast of England before he moved to London. He explained to Artist Direct: "It was literally about sirens and living in the city. I lived between a hospital and a police station so there were constant sirens. It explores the idea that when you live in a city, sirens become a sort of subconscious thing that eventually you come to ignore. There was a moment when I heard one, and it had a poignancy I'd never heard before. I tried to get that poignancy into a song. Although we come to ignore sirens in city, they're quite a cry. They represent something that doesn't relate to the songs you come to ignore. Essentially, something bad is happening. Someone is in trouble. For that one person, it means a lot more than it does to you. It's about being in a city. It's about being lonely. It's about trying to understand it. I had the lyric as a song idea, and I finished it off when I moved to London."
• In 1819 the French physicist Baron Charles Cagniard de la Tour developed an acoustic instrument, which could be used to produce musical tones. De la Tour's siren could produce sound under water, suggesting a link with the sirens of Greek mythology; hence the name of the instrument. This developed into the modern loud noise making device used to warn of air raids, tornado, nuclear tests etc. as well as the sirens on emergency service vehicles such as ambulances, fire trucks and police cars.