Songfacts®:

• The title of this glitchy, hip-hop influenced song refers to the Sex Pistols' Sid Vicious and the tumultuous relationship between him and his American girlfriend, Nancy Spungen. Vicious was arrested for Spungen's murder, but died of a heroin overdose before he could stand trial.
• This was the song on Sacred Hearts Club that took the longest to get right. Mark Foster told HMV.com: "We beat our brains over 'Loyal Like Sid and Nancy.' The music went through a lot of iterations before we finally settled on a three act play sort of format. But I went particularly insane writing the lyrics to that one. Also, it was important to me that the vocal delivery was right. I didn't want to ever come across like I was trying to rap. The vocal needed to be sensual to offset the aggression of the lyrical message and the beat."
  
  "I probably sang that song 500 times until I could wrap my head around how to make the vocal delivery assertive but still feminine," he continued. "The political message posed another challenge. 'How do I write this song without sounding like a preacher on a soap box?', kept running through my head. Especially when it came to touching on issues like the murder of Eric Garner and Black Lives Matter. And the new US policy on accepting refugees. It was a delicate dance to get these points across in the right way."
• About halfway through the song Mark Foster segues into a spoken-word piece, complete with an ominous bass line, which is a tribute to Gene Wilder's memorable lines in Willy Wonka and the Chocolate Factory. "We were totally referencing that [moment in the film]," Foster told The Independent. "Actually there was a different variation of the lyrics... so the beat dropped and we actually did this:"
  
  (Sings): "A world of pure imagination, take a look, and you'll see/into your imagination."
  
  Foster continued: "And then the beat came back in, 'duh duh dom', and there was this instrumental string thing. We played with it for a few days then ended up scrapping it."
• Mark Foster wrote the song with Foster the People multi-instrumentalist Isom Innis. "It was originally this atonal kind of beat that you hear in the verses, like an atonal dance track," Innis explained. "Mark took it in the studio, added a chord progression, arranged a song that was really meant to be in the dance world. And that's when it started to transform."