"Lily Allen" did not originally perform "Somewhere Only We Know." The song was originally recorded by the British band Keane for their debut album "Hopes and Fears" in 2004. Lily Allen covered the song in 2013 for the John Lewis Christmas advertisement. Her version was a commercial success, reaching high positions on music charts. The song's gentle and emotive melody, combined with Lily Allen's interpretation, brought a new dimension to the already popular track. It's an example of how different artists can reinterpret and bring their unique style to well-known songs.