Taylor Swift and Calvin Harris break up: Why the relationship failed to work out

Taylor Swift and Calvin Harris's break-up, after a 15 month relationship, has left fans puzzled. The former couple's sudden split – reportedly last seen holding hands in New York at the weekend – has left some unanswered questions. Particularly in the aftermath of Harris's 21 May car accident which saw Swift skip the Billboard awards to be by his bedside.

A case of 'just good friends' may be the answer as, according to E! News, the Blank Space singer and the Scottish DJ's romance had just fizzled out. Allegedly it was Harris (real name Adam Wiles) who broke up with the 26-year-old pop singer.

"This all happened last week," a source said. "Taylor and Adam [Calvin Harris] had no big blowout fight, but the romance just was not there anymore for them. Adam is the one that ended it. It was all done in a very mature fashion. Taylor is pretty upset but they are still in communication."

"Adam really liked Taylor, she was not the type of girl he ever dates and he liked that. He liked how innocent Taylor was and that she had a good caring heart. Taylor's heart was more in it then he was. He started to lose interest over the past few months, but really tried to not just break up," another source said.

The two were "more friends than lovers" and were "just not very compatible in different areas in their relationship", the source said. "The touring and traveling didn't help."

"Taylor and Adam had very different group of friends," the source said. "He [Calvin Harris] did not cheat on her at all. Just not a good match."

"She was in Nashville with her family and they have been helping her through the break up," another source said.

"Taylor was really disappointed in Calvin and felt like he wasn't there for her. The relationship wasn't progressing the way she wanted it to. She felt like he wasn't taking it seriously enough and wouldn't come through for her when she needed him most. She felt down and like her needs weren't being met. She doesn't want to get back together," the source said.

As of now, Swift and Harris have not commented on their split.