Sam Smith's James Bond theme song has topped the charts in the U.K., making history as the first Bond theme to reach number one in the country. Smith's single "Writing's on the Wall" is featured in the upcoming film "Spectre."

"Out of all the songs I've brought out in my life, I was not expecting this to even chart in the top 10, let alone number one. It's unbelievable," Smith told BBC Radio 1 (via BBC News).

"Writing's on the Wall" amassed 70,000 chart sales and streams - 13,000 more than Justin Bieber's "What Do You Mean?" Critically, the song has received mixed reactions.

"When the song came out I was so nervous," Smith said. "It's impossible to bring out a Bond song that pleases everyone."

He continued, "Everyone's had mixed reviews when they bring one out, but the charts don't lie and people seem to love it and enjoy it and that's just the most magical thing."

The previous highest charting Bond themes were Adele's "Skyfall" (2012) and Duran Duran's "A View to Kill," which both reached number two. Paul McCartney's "Live and Let Die" peaked at number seven.

Adele's song was released midweek, putting her at a slight disadvantage to Swedish House Mafia's number one song "Don't You Worry Child." "Skyfall" eventually went on to win a Brit award, a Grammy, a Golden Globe and Best Song at the Oscars.