John Singleton sold his ad agency last night, on the eve of celebrating 50 years in the business.

Mr Singleton sold his remaining parcel of 18 million shares in STW Group and pocketed over $50 million from the sale.

Singleton, who went from working in the Sydney mailroom at J. Walter Thompson in 1958 to become the face of the industry, told The Australian that years of holding a minority interest in the company he founded had finally taken its toll.

He will focus his attention on his other businesses, ranging from thoroughbred sales to brewing and lingerie.

However, Mr Singleton tipped that he may now focus on expanding his media empire, building on his interest in Macquarie Radio.

He said the decision to abandon the advertising industry completely was driven by a comment that he would be celebrating 50 years in the business next year.

“Some silly bugger said I was going be celebrating 50 years in advertising next year, so why don’t we have a party. I figure 49 is a good time to get out.”