The Herald on Sunday is legally prevented from naming the man because it could lead to the identification of the man's accomplice - another career criminal with more than 130 convictions - who has name suppression.
However, the newspaper is preparing to release its information to police.
Sources said police already knew the identity of the two men and were "hot on their trail" but could have difficulty gathering sufficient evidence to pin the men to the crime.
In October, the second of the men, who can be referred to only as "W", offered to repatriate a Goldie painting and other artefacts stolen from the University of Auckland in return for a lesser sentence on fraud charges.
Police then arranged for minor charges against the man to be dropped in exchange for the return of the 1920s painting Planning Revenge, a copy of the Oxford Lectern Bible and a set of seven Colin McCahon poems stolen from the university.
They were stolen from its library during the 2005 Christmas holidays and a $20,000 reward was put up by the London insurers of the painting, through investigators GAB Robins.
Auckland lawyer Chris Comeskey, who arranged the deal for the return of the medals, also brokered the Goldie deal, but it is unclear whether any reward was paid out.
Six weeks after arranging for the exchange to take place, "W", working closely with his accomplice, is suspected of breaking into the Waiouru Army Museum and stealing the war medals. Three days later "W" was back in court on fraud charges and taken into custody, where he has remained since.
Some reports have suggested that while in Mt Eden Prison, "W" was in contact with leading gang figure Daniel William Crichton, who last week claimed he received a bail-for-medals deal from police after negotiating with the thieves.
Comeskey would not comment on this, but sources close to the case rubbished that theory, saying Crichton had no involvement in the return of the medals.
"He's clearly embellishing his role in the whole thing," a source said. "Chris was the first person to find out about this." Another source said Comeskey had been negotiating for the return of the medals days after they were stolen and Crichton was trying to use the medals as a way of getting a reduction in his sentence on serious drugs charges.
Last week, Comeskey told the Herald on Sunday he had used his contacts in the criminal underworld to locate the medals. He also spoke of the day the medals were returned, and what it meant to him. "Holding the Upham medal in my hand, knowing what it signified, was something else." He clarified a line in last week's Herald on Sunday, saying he was "as nervous as the day my kids were born".
He did not want to discuss the role of "W" or his accomplice, saying he was tired of the matter.
"W" was eventually sentenced this month to 27 months' jail on the fraud charges, with the case's judge criticising the man's attempts to lessen his sentence by arranging for the return of the Goldie and other artefacts.
