Katy Perry and proposal at Auckland show: This is how we do

An elaborate proposal plan paid off for a Melbourne man who followed his girlfriend to New Zealand to propose to her on-stage at the last show of Katy Perry's world-tour.

Stef Chin was in Auckland to see Katy Perry perform after following her around the world during her Witness: The Tour.

Her boyfriend, Grant Alexander, told her he was still in Melbourne but in reality, he had flown to New Zealand to propose at Perry's show.

He arrived in Auckland on the morning of the concert and, with the help of Chin's friends, managed to sneak around the city all day without bumping into her.

Before the show, he was taken backstage by Perry's team and given a Left Shark costume by Perry and a seat near the sound desk at the back of Spark Arena to hide.

"She was getting her hair and make-up done and we had a little chat, she asked me how I was and if I was nervous.

"Each time Katy would come down the stage I would zip up the onesie at risk of getting on the big screen"

"Katy would look over at me dancing and give me a smile or a wink during the performance," Alexander explained.

The happy couple Grant Alexander and Stef Chin with Katy Perry. Photo / Supplied

Selected from the crowd at "random" after the song Wide Awake, Alexander had the hood of the costume zipped-up so he wasn't recognisable.

Once on stage Perry gave him a mic and asked if he wanted to bring anyone on stage, to which he replied "Stephanie Chin".

"He's such a sly person," Chin said.

"He dropped me off at the airport and said have fun in Auckland ... I didn't know he was going to be there."

Once onstage Alexander gave a heart-felt speech he prepared on the flight over before asking the magic four words.

I JUST GOT PROPOSED TO ON STAGE WITH KATY OMFG WTF @xander85

— Lili/Stef ♡ (@lilithia) August 21, 2018

"I might just be a lucky left shark, but you're the right shark for me ... will you marry me," Alexander said.

Much to the delight of the crowd at Spark Arena, she said yes.

She told the Herald it was an easy answer.

"It'll be eight years this December that we've been together, not only was I not going to say no, it was about fricken time," Chin said.

Perry then asked the pair to sit on stage while she sang them her new song, Into Me You See.

"What I'm about to sing is a love song and I wrote it for my boyfriend," Perry said before singing to the couple.