A convicted German computer hacker is believed to be the secret buyer of the $30 million Chrisco mansion.

The Coatesville property, considered New Zealand's most expensive house, has been vacant since Richard and Ruth Bradley, the British founders of the Chrisco Christmas Hamper fortune, relocated to Sydney nearly two years ago.

A source who wishes to remain anonymous said Kim "Kimble" Schmitz, 36, was the man behind an arrangement including a long-term lease of the 24.3ha estate, and sale once the lease expires.

The Finnish flag flying from the house last week, was "a disguise".

The source, who knows Schmitz, had heard he was interested in the mansion a few months ago and had recently been told Schmitz had entered into an agreement for the property with the Bradleys.

Schmitz rose to fame in Germany in the 1990s as a teenage internet tycoon, who eventually received a two-year probationary sentence for hacking into corporate computer systems and accepting gang-related stolen goods.

He also had to pay a €100,000 ($195,000) fine for what was then Germany's largest insider-trading case. Newspaper reports said that after his arrest he made his fortune by investing in tech stocks and selling a majority stake in an internet security company, DataProtect.

The company filed for insolvency shortly after.

In 2001, Schmitz provided more than $1 million of his own money to help the flailing web company LetsBuyIt.com, but was arrested the following year for his alleged involvement in the "fluctuating fortune" of the Dutch company.

According to the Independent, Schmitz was deported from Thailand and arrested at Munich Airport, where he called himself the "Royal Highness Kimble the First".

His now seemingly defunct website www.kimble.org once provided details of his extravagant life - including images of his cars, his yacht and the Playboy models he surrounded himself with.

Discussion on internet forums questioned the authenticity of the images.

Weighing a hefty 136kg, Schmitz has been called one of the world's "largest tech entrepreneurs".

He is believed to be living in the penthouse of a Hong Kong hotel - and to have started an investment company called Trendax - but travels between Dubai, Australia, Germany and the Philippines.

The Coatesville mansion was completed in 2006 and features a tennis court and a lap-pool.

Last week labourers working on the property said no one would be occupying the house for "a couple of months".

The sale price is not known.