Eilish is the youngest singer ever to record the theme for the Bond franchise, having just turned 18 in December last year. She co-wrote the song with her elder brother Finneas O'Connell.
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The dark, atmospheric song shows Eilish's voice in a different light to her normal music, hitting high notes over a piano and gentle brass.
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Eilish's ballad was released at the same time as the latest trailer for No Time To Die, which tells the story Bond's mission to rescue a kidnapped scientist. The film will be released on April 3 and is Daniel Craig's final outing as 007.