Billie Eilish has confirmed that there is a hidden treat for James Bond fans in her theme song for No Time To Die.

Eilish dropped the Bond track in early 2020 to coincide with the film’s original release date that April. Due to COVID-19, however, the film has been delayed multiple times, and will finally see its European release on September 30.

• READ MORE: Billie Eilish takes the stealth approach on Bond theme ‘No Time to Die’

Grammy-winner Eilish has now encouraged her fans to listen back to the song and discover an Easter egg that may have been missed first time around.

“You can’t do a Bond song without it sounding like a Bond song,” the singer told the Bond film’s official podcast. “If you listen closely, you can hear [the classic Bond opening sting] in the second verse.

“It’s very subtle and it’s very echoed. We decided to do that though,” she added.

Eilish’s brother and long-standing producer Finneas O’Connell also went into some detail about how the track was recorded.

“It was recorded in London, and then like there was a version without [the Bond sting]. Then, we were like, put it back in, it’s great. Then, Johnny Marr plays all the guitar,” he explained.

“That was just like a [thrill], especially his line in the chorus and the part at the end, to us, were like no-brainer moments, really. It’s just exactly what it needs here.”

In late 2020, composer Hans Zimmer shed some light on how Eilish came to be the voice of the latest Bond theme.

He explained that there were a “box of songs” that were in the running for the theme song, including “this small, leanly produced, very personal song by Billie”.

“I just went, ‘That’s it,’” he told GQ. “And everybody said, ‘Well, but it’s not quite right. It’s not good.’ [I said] ‘No, no, no, here’s the mistake you’re making – she and Finneas haven’t seen the movie yet. They don’t know what they’re writing about. Get them on a plane, get them over here.’”