Shadbolt was drawn into politics while studying at the University of Auckland where he was a member of the students' association executive and edited uni rag Craccum.
He joined a left-wing youth movement and was arrested 33 times during political protests, once for using the word "bullshit".
Shadbolt went on to become a concrete contractor before running for the mayoralty of the former Waitematā City in 1983.
He won – and infamously celebrated his election by towing a concrete mixer dubbed "Karl Marx" behind the mayoral car in a Christmas parade.
It's something people still remind him of - regularly. "I have to be honest now and confess that I used Ready Mix like every other contractor in the country," recalled Shadbolt.
"But for some reason people love that image of the rusty old concrete mixer and the huge eight-seater Daimler which came from the British High Commission in London."
The Waitematā mayoral stint ended in hullabaloo - with a failed audacious stadium bid and missing mayoral chains all now part of the folklore.
After a few false starts it was in 1993 that Shadbolt boldly made his way to Invercargill and won a widely contested race, beginning a love affair with the southern city which is clearly mutual – he's now serving his eighth term in office.
Introducing the Southern Institute of Technology's Zero Fees scheme is his proudest achievement, yet it's relating to people that has given him the most delight throughout his mayoral career.
"It's some of the fringe activities, doing charity work, or having lunch with 180 people at Christmas … and just seeing how happy people are to attend that gives me a lot of joy."