He's been One Direction's biggest supporter and even counts Harry Styles among his best friends.
The drama began when Louis posted a completely innocent tweet about not being able to leave his hotel room because of the number of paps.
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He wrote: ''It's a beautiful day and we can't leave the hotel. #papsaretwat
But it seems that Grimmy took exception to the innocuous post and appeared to reference it on his radio show later in the day.
He said: ''I love a complainy popstar. It's my favourite thing. All complainy. 'I can't go outside because I'm famous'. Mask. I'm gonna wear a [RadioRead More »from Louis Tomlinson blasts Nick Grimshaw in Twitter rant after he calls him 'complainy' - don't tell Harry Styles!