Sam Smith has confirmed he'll sing the next Bond theme tune.

Fans have been speculating for months now that the 23-year-old British crooner will be behind the song for next 007 instalment Spectre.

After previously denying the gossip, Sam has now revealed he really is the next musician to lend his vocals to the spy franchise with track Writing's On The Wall.

"This is one of the highlights of my career. I am honoured to finally announce that I will be singing the next Bond theme song," he wrote on Instagram.

"I am so excited to be a part of this iconic British legacy and join an incredible line up of some of my biggest musical inspirations. I hope you all enjoy the song as much as I enjoyed making it. You can pre-order 'Writing’s On The Wall' on CD or vinyl using the link on my profile, or on iTunes from midnight. (sic)"

Sam had already made his involvement pretty clear yesterday when he posted a picture of his hand on Instagram, showing off a silver ring with the octopus Spectre symbol on his middle finger. He didn't caption the snap, but followers immediately cottoned on.

And this morning he spoke about the job in more detail, revealing the recording process.

"I'm so relieved to actually talk about this, this has been a top secret mission of my own. I got called into the office with Barbara Broccoli and Sam Mendes and they gave me the script, I read the script... they said 'have a go at the song,'" he explained to BBC Radio 1.

"It's the quickest I've ever written a song - it took 20 minutes... and they loved it! I love the song so much."

Sam follows in the footsteps of iconic musicians, with Adele crooning Skyfall's theme tune in 2012 and Madonna lending her voice to 2002's Die Another Day.

Writing's On The Wall will be released on September 25, while Spectre hits cinemas from October.