Exes Taylor Swift and John Mayer attend Drake's birthday bash

Taylor Swift had a couple of awkward encounters at Drake's 30th birthday bash on Sunday night (23Oct16) when her ex John Mayer and music rival Katy Perry showed up.

The 26-year-old pop star attended the party at Delilah's in West Hollywood alongside pals the Haim sisters and Karlie Kloss and her brother Austin Swift, but she didn't expect to see Mayer, the subject of her break-up song Dear John, there - or her pop nemesis Katy.

He and Taylor did not part as pals, and he told Rolling Stone magazine the song she wrote about their break-up left him feeling humiliated.

"I never got an email. I never got a phone call," Mayer told the publication. "I was really caught off-guard, and it really humiliated me at a time when I'd already been dressed down. I mean, how would you feel if, at the lowest you've ever been, someone kicked you even lower?"

Ironically, Perry also dated Mayer, but reports suggest they ended their romance on good terms and remain friends.

They were an on-again/off-again item for a year before Katy started dating actor Orlando Bloom in early 2016.

A source tells E! News that Perry and Mayer chatted at Drake's bash and appeared friendly and peaceful, while John and Taylor avoided each other.

Fellow guests included French Montana, Jamie Foxx, Zoe Kravitz, Shay Mitchell and more.

Drake, who turned 30 on Monday (24Oct16), celebrated his birthday over the weekend by announcing the release of a new album, More Life, which will be available in December (16).