A PSA (Prostate-Specific Antigen) test followed by a biopsy confirmed a diagnosis of aggressive prostate cancer.
"It wasn't great to hear that," Wallace recalls of his dad's news.
"Me and Dad have always done everything together. We've always been the best of mates, ridden dirt bikes together and quad bikes ... the good news was even though it was an aggressive cancer, we got it early."
Thankfully, Barry did not have to go through chemotherapy. After having surgery to remove his prostate, he was put on inhibitors - drugs to keep the cancer under control. A year and a half later, he underwent radiotherapy after a little bit of cancer spread to his hip and he's now in remission. But the treatment still takes a toll.
"He's an old bastard," Wallace jokes before sharing it was Barry who encouraged his son to go and get checked too.
"He pointed out the fact that I am also an old bastard now, turning 41," the radio host says.
After an online consultation, Wallace learned that if prostate cancer has occurred in your family, you are twice as likely to get it. It's twice a very small number - but around 4000 Kiwi men are still diagnosed with the cancer every year.
"If you do have an increased chance, you do everything you can to keep yourself out of that group of people," Wallace says.
"It would be foolish to have a family history of prostate cancer and not be proactive about doing that.
"So there was the finger, and there was the PSA test, and a camera crew with me - which is the story of my life!"
Wallace shared the footage of his check-up to his Instagram page in the hopes it would encourage other men to go get their prostate checked.
"It's a non-event. You go in there and it takes you by surprise, but really it's no more annoying than getting your haircut, but you have your pants down."
It's that "non-event" that saved Barry's life, he says - and it's the reason he gets to spend time with his beloved grandchildren today.
"Dad would have missed out on all three of my kids," Wallace says, adding that Barry probably "wouldn't have believed" he and Sarah would become parents to twins.
"He would have missed out on the fact that I had twins. He comes in the door and Sienna comes running up to him and gives him a big cuddle. You can't even explain how important those moments are."
"I don't want to miss out on that, it's so important," Barry agrees.
"One of the common questions is, 'what do you want for your birthday?' and the answer is, 'another birthday'."
Wallace's "full man check-up" also revealed his cholesterol and blood pressure were up, so now he's on a full over-40s health plan.
"I'm really adjusting my diet and how much I'm drinking. Since having the girls and having this health check, I'm going to do everything in my power. I don't want to miss out on a single moment of my kids."