The album, the band's fourth studio record, sold 96,000 copies in its first week on release, scoring the highest first-week sales for a U.K. girl group since 1997, when the Spice Girls released Spiceworld.

"Four albums down the line & you've only gone & got us our FIRST EVER Number 1 album," the singers write on Twitter. "Your reaction to #GloryDays has been b**ody amazing!".

"We say it all the time but we really do have the BEST fans in the world & we (love) you to the (moon) and back! LET THE #GLORYDAYS ROLL(love) the girls x," they add.

Little Mix's chart-topper forces Metallica to settle for two with Hardwired to Self-Destruct, while Bruno Mars takes third place with 24K Magic.

Michael Ball and Alfie Boe's Together and Elvis Presley's The Wonder of You round out the top five, respectively.

Meanwhile, on the singles chart, Clean Bandit's Rockabye comes in at number one, while Rae Sremmurd and Gucci Mane's Black Beatles takes the second spot, thanks to its popularity with social media's Mannequin Challenge.

Little Mix's Shout Out To My Ex is at three, ahead of James Arthur's Say You Won't Let Go at four, and Maroon 5 and Kendrick Lamar's Don't Wanna Know at five.