Sir Michael Fay, one of the country's richest men, has swapped the bank for the barnyard and bought a $9.2 million slice of New Zealand's dairy heartland.

The investment banker and island owner now lists "farmer" as his occupation when filling out immigration forms.

Sir Michael flew by helicopter this week to buy Broadlands, a 533ha dairy farm 30km north of Taupo. He said after years of being tied to the day job, he and business partner David Richwhite were finally able to enjoy the fruits of their labour.

"We are like a couple of grown-up kids who are finally able to have the time to do what we want," he said from his home at Great Mercury Island.

"I have been living back in New Zealand for some time and got rid of the shackles of being attached to my desk job all day. I looked at the rural sector and decided to significantly increase my investment."

Richwhite has a career in music management in London, and Sir Michael's daughter Annabel has become a pop star.

Sir Michael is said to have flown in by helicopter to inspect the farm and bid personally at a packed auction on May 19. Bidding began at $5m and it sold for $9.2m.

Sir Michael said he had invested in farms in 1977 and was forced to sell previous dairy farms after the 1987 stockmarket crash. "It's always been a passion of mine," he said.

Sir Michael said he saw the farm as a long-term investment.

He said he hoped his children would one day take ownership of the property but they hadn't inherited his love of farming.

He planned to take a hands-on approach and manage milk production. "I am still fit and healthy and I enjoy the aspects of running the farm," he said.

The property - which includes a three-bedroom villa, and more than 130 paddocks - was in receivership.

A farming consultant said Sir Michael had bought an "underperforming asset when the market is in a quiet phase".

"If he invests $1.2 million in it and sells it he could turn a tidy profit," the consultant said.