The 23-year-old singer had been rumoured to have written the song about Harry, 19, after the two briefly dated in secret last summer before trying to make a go of things again later that same year.
In an interview with weekend’s Times Magazine, Taylor was asked about what it was like performing the song at the BRITS earlier this year.
She revealed: "You're balancing the analytical side of your brain, which is telling you where to go and how to go there, with the other side of your brain, which is saying 'Feel everything you're singing, and show it on your face.
“Feel everything exactly as you felt it when you wrote the song."
The interviewer then went on to ask if she would ‘die’ if she had to sing a song she’d written about an ex-boyfriend in front of them.
Taylor then admitted that she had already been in that situation when performing 'Trouble' at the BRITS.
She said:"Well, it's not hard to access that emotion when the person the song is about is standing by the side of the stage watching."
Now we don’t recall any of Taylor’s exes being in the audience at the BRITS when she performed- other than Harry Styles that is.
Which, by the power of deduction means that ‘I Knew You were Trouble’ WAS written about Mr Styles.
Serial song writer about her exes Taylor, also denied the rumour that she kept a trunk full of keeps sakes previously owned by her past boyfriends to help her write songs.
She said: "Yeah, I read that and it really creeped me out."
[Related article: Harry Styles gets over Taylor Swift with some partying]
[Related article: Did Taylor Swift write 'I Knew You Were Trouble' about Harry Styles?]