"Firstly I wanted to get fit, secondly, we wanted to pull together all the different business units that Downer has in Northland and thirdly and most importantly, to raise money for charity," he said.
Both companies have used their commercial contacts to raise a pot of money for each of the 12 fights - the winner will get two-thirds for their charity while a third will go to the loser's charity. Downers is supporting Kidney Kids and Fulton Hogan is supporting North Haven Hospice.
A trophy will be the biggest prizeat stake for the two teams, accompanied by smaller prizes for a host of competitions such as the biggest loser, with a prize going to the fighter who has lost the most weight in the 13 weeks of training.
"Ultimately we are not doing this because we are rivals or because we don't like each other, we are doing this because as companies and individuals we are both committed and passionate about helping the community that we live in," Flower said.
He said there had been plenty of pain in the build-up.
"The physiotherapists have been making a fortune out of us; there is a list of injuries as long as your arm. I've strained my Achilles, hurt my shoulder and my elbow and my neck is the latest - I can't wait to get in the ring and get the training over with," he laughs.
The night's card is at ASB Stadium Kensington at 7pm.
