Katy Perry and Justin Bieber are fans of One Direction

Katy Perry has con­grat­u­lated One Direction's Niall Horan on his band's US iTunes chart Number One success.

Katy, who ori­gin­ally audi­tioned Horan for The X Factor, tweeted: "@NiallOfficial con­grat­u­la­tions, you didn't let me down! xo." Back then she warned him "like­able­ness isn't going to sell records, it's talent. And you have…a seed of it", before putting him through to bootcamp.

The 1D frontman replied: "Thank you for putting me thru!we've been working hard,I won't let you down."

Perry wasn't the only one for­ward­ing on her good wishes, Justin Bieber also tweeted Niall to say: "good guys always win bro. congrats."

'Up All Night (Deluxe Edition)' and 'Up All Night' are at Number One and Number 2 respect­ively  on the US iTunes album chart.