They're the only girl-band to be crowned winners of The X Factor.

The ladies were back on the stage where they found fame on Sunday evening. https://twitter.com/glossperrie/status/937415078936268800 And suffice to say that they blew everyone away with their incredible performance of their biggest current hits. The group features singers Perrie Edwards, Jesy Nelson, Jade Thirlwall, and Leigh-Anne Pinnock and were also joined for the performance by Latin American band, CNCO. https://twitter.com/LaraInCornwall/status/937403951992967174 Even difficult-to-please Simon Cowell was in awe, afterwards gushing: "That's what I call a masterclass! I feel so proud right now. You came on the show, you won the show, you became the biggest girl band in the world and you did it your way." https://twitter.com/TheXFactor/status/937403216102338562 Understandably, Twitter was alight with compliments as a result - with countless fans declaring their admiration for the band, who won the reality TV talent show back in 2011. https://twitter.com/ITV/status/937404021505187840 The band's latest album, Glory Days, sold almost 100K copies in its first week of release in the UK - where the four ladies all hail from. https://twitter.com/elliot_gonzalez/status/937403953981067265 Sam Smith also performed on Sunday evening on the X Factor; he sang One Last Song. https://twitter.com/OnTheJoSlow/status/937403755515072513