The Stay With Me star unveiled Writing's on the Wall, which accompanies new 007 movie Spectre, earlier this month (Oct15) ahead of the release of the latest film installment.

Sam scored a number one in the U.K. with the track, marking the first time a Bond theme has hit the top of the British charts, but he also faced a mixed response from fans, with some praising the song's "haunting" qualities while others branded it the "worst Bond theme ever".

The singer admits he was not prepared for the criticism he faced, but insists he does not feel hurt by the nasty comments because he still managed to hit the number one spot.

"(Recording the song) felt like a dream come true for me, but I was very naive about the whole thing, because I love the song, so much, still love it," he tells Britain's BBC Radio 1. "I was feeling really confident about it - and I still feel confident about it - but when I released it, I was very naive and I thought everyone would love it. But Bond, it's impossible for everyone to like a Bond song.

"The fan base, they're mental, so that initial release with the mixed response, I was like, 'OK, just finding my feet'. But when it went to number one, it was just unbelievable, it was amazing."

During the chat with DJ Annie MAC, Sam also revealed work on his upcoming second album is going well as he has already written four tracks and decided on a title for the record.

"I genuinely thought this was going to be the hardest album - it still could be - but I refuse to think like that because this is what I do and what I love to do," he adds.

"I write love songs and I'm forever going in and out of relationships and wanting to say things about life and love, and if I had nothing to say over the last year then that's mental because so much has happened to me."