The 96-year-old, who loves the cut and thrust of retailing as well as big game fishing, will mark  another milestone in an extraordinary business career on Wednesday when vacuum cleaner group Godfreys lists on the Australian Securities Exchange in a $78million float.

Mr Johnston is the largest shareholder in Godfreys, a business he  joined in 1936 when it was in its infancy. "It's been my life," he said.

"That and fishing are the two things I love," he said.

But Godfreys, which has 209 stores and is the market leader in the $1.3billion cleaning products segment, isn't the only business in which he has an interest. He holds a stake in the Shaver Shop chain of 76 stores, and is a  shareholder in the parent company that owns footwear and clothing brands Diana Ferrari, Mathers, Williams and Colorado. The parent entity of those brands is Fusion Retail Brands, previously  Colorado Group. Colorado Group went into receivership in 2011.

Mr Johnston steers clear of the limelight and lives a quiet life in Adelaide, but  gets out on the road to talk to Godfreys store operators and staff when his health is up to it. He was at a Godfreys store in the Adelaide suburb of St Marys  on the day the float was officially announced on November 25.

He does business on a handshake. It was how he started at Godfreys in the 1930s and how his relationship with the current chief executive of Godfreys, Tom Krulis, began 30 years ago. Mr Krulis said  Mr Johnston has been a fantastic mentor.

Godfreys began in 1931 in Melbourne when Godfrey Cohen started selling vacuum cleaners after first selling sewing machines from home as a 14-year-old. Johnston became a partner in 1936. Several decades on, Krulis and Johnston met when Krulis married into the Cohen family and shifted from Sydney to Melbourne. Johnston could see the potential in Krulis, who was a corporate lawyer at the time.

"He told me to go and sell vacuum cleaners for four years first," Mr Krulis said.

Private equity firms Pacific Equity Partners and Unitas Capital paid $300million for Godfreys in 2006, buying it from Johnston and the other  shareholders. But it was laden  with  debt and when the global financial crisis hit  in 2008, the business struggled. Johnston and investment bank Nomura bought it back for just $100million in 2011.