Broadcaster John Campbell has resigned from RNZ to take up a role with TVNZ.

John Campbell has been hailed as a mentor and expert storyteller as he signed off for the final time on RNZ National.

The veteran journalist joined RNZ in 2015, tasked with reinvigorating the station's evening news show Checkpoint.

He presented 650 episodes of the simulcast radio-television show, newsreader Katrina Batten said as she read the final news bulletin with Campbell on Friday night. She had been with the show since it started in January 2016.

The final 20 minutes of Friday's show were dedicated to celebrating the outgoing host. He had resigned from RNZ in favour of a new job offer at TVNZ.

Phil Walter/Getty Images John Campbell starts his new job at TVNZ in two weeks.

RNZ journalist Alex Perrottet​ would be taking over Checkpoint presenting duties for a month. Ex-Newshub journalist Lisa Owen would then take over the role.

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Friday night's episode finished with Perrottet singing a tribute to Campbell.

"You waved the white flag when you came from TV, then dragged us to millennium three," Perrottet​ sang, in reference to the digital-focus Campbell brought to the show.

RNZ John Campbell reporting for Checkpoint

He arrived at the public broadcaster alongside his Campbell Live colleague Pip Keane. Their arrival saw major investment in video, with Checkpoint becoming "radio you can watch" on television and online. However, RNZ's video capacity remained limited.

Most of the stories broadcast on Checkpoint used still images or were filmed and edited by solo-reporters, rather than videographers.

As he prepared to broadcast his final show with RNZ, Campbell told Stuff he was forever grateful to the public broadcaster. It was an emotional last day, filled with cake, he said.

"Once I start eating sugar, I have to keep eating it," he says. "Or, I will burst into tears."

Claire Eastham-Farrelly Lisa Owen (centre) will replace John Campbell on Checkpoint.

When he starts his new, roving reporter job at TVNZ next week, Campbell will leave behind his tight knit Checkpoint team, including longtime executive producer Keane.

She would be moving into a new senior management job at the expanding RNZ, but Campbell admitted saying goodbye was hard.

"Pip is a force of nature, I mean she just gives it everything she's got and totally gives a damn," Campbell said.

They have been working together for nine years. When it came time in June for Campbell to tell everyone he was leaving, he said it wasn't easy by any means.

"It was a tough chat, and I am sorry to be leaving," he said on Friday morning. "But everyone understands why I am leaving."

Campbell started reporting in 1989, as one of RNZ's last batch of cadets. "I got in, sort of by accident," he said. But now, "I can't do anything else".

After cutting his teeth at RNZ, he moved to TV3 where he stayed for about 24 years. There, he fronted 3 News and Campbell Live. For most of his career, Campbell had been kept in studio.

In the end, presenting was tiring and he said his focus had turned to meeting real people rather than sitting in studio.

"There's a part of me that longs to not have to race into studio each night, to be able to go and stay in the field."

TVNZ offered him "a sort of fusion job", Campbell said. He would be a fill-in presenter for all of the network's current affairs shows. "But I will only be a fill-in," he stressed. Most of his time would be dedicated to reporting.

Already, Campbell had spots lined up on Breakfast. His first appearance on TVNZ was expected to be on the Sunday programme.

Former Newshub journalist Lisa Owen would take over the Checkpoint show, which would remain a simulcast radio-television broadcast.

Of his time at RNZ, Campbell said one of his biggest successes was reaching an audience "who probably don't even know where RNZ is on the dial". Its Facebook page had more fans than the main RNZ page itself.

The work it did was hugely important, Campbell said, and would continue to be.

"Checkpoint will continue without me. They will continue to be superb and give a damn without me, they don't need me."