"I think my aspiration back then was to buy a $40 Mambo T-shirt," he said, with a laugh.

Now the dad-of-three and proud Canberran is the owner of four McDonald's in the national capital - at Manuka, Weston, Westfield Woden and, the newest, in the Monglo Valley which opened last year.

From that teenaged kid with a part-time job, Mr Carroll eventually rose to become general manager of four stores in Wagga and then bought stores in Leeton and Temora before moving with his family to Canberra in 2015. He and his wife Kate had bought real estate when they were still teenagers and used the capital from their property investments to buy their first McDonald's in 2010.

The couple has three children - Hunter, 11; Milla, nine; and Elsie, six.

"Canberra's home now," he said. "Coming from Wagga, Canberra is like a big country town, with the benefit of living in the city. We love it."

Mr Carroll said Canberra was lucky to avoid much of the brunt of COVID-19, but the business of Maccas had changed.

"We're pretty lucky that we've got a lot of policies and procedures in place and we're pretty resilient to be able to change quickly, and be nimble, and make customers feel safe with sanitisation and food safety," he said.

"Delivery has really increased. What was once a very small percentage of the business is now a large percentage. Drive-through, obviously, has exponentially grown and rooms now and playgrounds are just big open spaces. I can be sitting here at lunchtime and be the only one here, but drive-through will be busy. Consumers' behaviour has just changed."

Mr Carroll's greatest satisfaction came from mentoring his 450 staff and giving back to the community.

That giving back includes McHappy Day on November 14 for Ronald McDonald House charities, with $2 from every Big Mac sold on the day going to the home-away-from-home for seriously ill children and their families. Silly Socks and Helping Hands are now available in stores.

"When you have kids and hear [the families'] stories, it just resonates so strongly," Mr Carroll said.