The 40-year-old singer and songwriter dated the 'Roar' hitmaker on and off for two years from 2012, and he has admitted five years down the line he still checks in on his former flame, and even tuned into her four-day YouTube video, which was to promote her fifth album 'Witness', and he even watched her sleep, although he has acknowledged the footage made him feel weird.
Asked if he tuned into the live stream on 'Watch What Happens Live with Andy Cohen' on Monday (27.11.17), he said: ''Yeah, I did. I think you'd have to watch all 96 hours to get the final verdict. That's her thing, man - to go big and bold. Yeah, I checked in with it. It's definitely odd to watch your ex-girlfriend asleep.''
But the 'Your Body is a Wonderland' hitmaker has no qualms about admitting to tuning in to the footage, and he has even encouraged people to admit to their actions.
He added: ''The way I see things now, I call it 'stand in the middle of the boat.' If someone says, 'I don't watch that,' it's like, 'Yes, you do.' You know? Watch when you want to watch it. Be human about it.''
And while John was honestly opening up about his activities, he also revealed he texted the 33-year-old artist to wish her Happy Birthday last month.
He said: ''It's like, if you want to text someone ... I texted Katy happy birthday. It was four in the morning. It was like a post-midnight, haven't-gone-to-sleep-yet, it's-technically-your-birthday send. Because how weird is it to be like, 'I want to say happy birthday now, but I'm going to wait until tomorrow afternoon?'. Be a person, man.''
Although Katy has hailed John as the greatest lover out of all the men she has been romantically linked to, including ex-husband Russell Brand and Orlando Bloom, the 'Gravity' rocker has not reciprocated the complement, but agrees with the 'Swish Swish' artist.
He said: ''Right here [pointing to his head]. So far, it's on a little SD card, I've been creating it myself. I've been my best lover so far.''
With the 61st Grammy Awards fast approaching, we have revised the long list of nominees once again and think we've made up our mind about who will be...
After a 21-year gap between albums and a full 19-year break as a band, Sleeper seem at last to be back in earnest.
Having announced her debut album 'When We All Fall Asleep, Where Do We Go?', Billie Eilish unveils a sinister video for her new single 'Bury a...
Imagine Dragons have now unveiled the official video for their single 'Bad Liar', following their recent animated lyric video.
Brit Award-nominated Tom Walker unveils the video for his newest single 'Just You and I' taken from his debut studio album 'What a Time To Be Alive'.
Stalker Miller have seen a will and determination come to fruition with the release of their debut album 'Homegrown By Joan'.
Audiences may be divided over whether this comedy crosses the line as it looks for...