Katy Perry "remained close" with Rob Ackroyd while she was dating John Mayer.
The 'Dark Horse' singer, who has reportedly reunited with the Florence and the Machine guitarist, stayed in contact with him after they briefly dated in 2012, even though she moved on with the singer-songwriter.
A source told E! News: "Katy and Rob are very close and have remained close since they broke up a while ago."
The 29-year-old beauty, who split from John in February after 18 months of dating, reconnected with 30-year-old Rob, who was linked to Alexa Chung at the beginning of this year, while in the UK for her Prismatic World Tour.
The insider added: "Rob has been in London for a while now."
The duo weren't shy about flaunting their romance at an afterparty to celebrate the end of the European leg of her worldwide jaunt last weekend.
A source previously said: "Katy and Rob seemed to be very much back together at her party on Saturday night.
"They were inseparable, kissing, flirting and cuddling away in front of the roadies, celebs and friends at the bash.
"There were a fair few famous faces in the room but Katy and Rob only had eyes for each other."
The rumoured couple were first spotted kissing at the Coachella Valley Music & Arts Festival in Indio, California in April 2012, but split a few weeks later, blaming their busy schedules.
Tagged in Alexa Chung John Mayer Katy Perry