A leading expert in recovering stolen and missing art said media coverage of the recent smash and grab style theft of two high-profile paintings had left them worthless to thieves.
Chris Marinello from Art Recovery International in Italy said the two Gottfried Lindauer paintings snatched from International Art Centre in Parnell, Auckland, were now "radioactive" and no one would buy them.
Marinello, an expert who had seen more than $500 million of art recovered, said last weekend's ram-raid theft of the two paintings was amateur and opportunistic.
"This was not an elegant robbery. It was totally unsophisticated by people who thought they would be able to sell the paintings quickly," he said.
"The level of interest and the publicity in the theft means these paintings are now radioactive - no one in their right mind will touch them."
Marinello is based at Art Recovery International's office in Venice but the company also works out of the UK and United States.
He has helped recover more than $500m of stolen and looted artwork and helped in the recovery of art taken by Nazis in World War II.
Just last year Marinello negotiated the return of a priceless 16th-century carving stolen decades earlier from a historic church in London.
A film crew were working with Marinello as he worked through locating seven high-profile stolen works.
Marinello urged New Zealand authorities to register the Lindauer theft and details of the artworks on the Artive.org register.
He oversaw the development of the Artive.org database which is considered the most technologically advanced system in the identification of stolen art.
The paintings stolen in the Parnell ram-raid were both by Gottfried Lindauer in 1884 and were known as Chieftainess Ngatai - Raure and Chief Ngatai - Raure. They were about to be auctioned, and were estimated to be worth $1m together.
Czech-born Lindauer trained at the Academy of Fine Arts in Vienna and migrated to New Zealand in 1874.
He became one of the most prolific and best-known painters of Maori subjects along with Charles Frederick Goldie.
Marinello said there was a possibility a ransom could be demanded for the paintings' return or they could be used to access drugs or weapons or as leverage in a "get out of jail free card".
He said the theft of the well-known paintings was unlikely to be an ordered grab.
If that was the case more care would have been taken, he said.
"We are not talking about stolen to order because of the way the smash and grab was done.
"My thought is it is common thugs looking to make quick cash."
Marinello said paintings in a window attracted smash and grab theft.
"It's the sparkle in the window - they take what they can and they are off."
He said the paintings could be recovered soon - or could take as long as a decade.
Most works were recovered, because it was harder to sell stolen art than it was to take it in the first place, he said.
"There is a bit of a black-market of course but they are offered for only about 5 per cent of their value."
Marinello said there was a market for the Lindauers overseas because they were attractive works of art and that was why the Artive.org register was so important.
If the pieces were recovered Marinello said their value would depend on damage done.
The high-profile theft of James Tissot's painting Still on Top saw it plummet in value.
The work was stolen from Auckland Art Gallery in one of New Zealand's most high-profile art heists. Ricardo Sannd, also known as Ricardo Romanov, walked into Auckland Art Gallery with a gun and cut the famous work from its frame in 1998.
The painting was found under Romanov's bed a week later but was so badly damaged tiny pieces of it were found on the gallery floor for weeks.
Although it will never be sold the painting went from an estimated $8m to an insured $2m.
Marinello said some works increased in value because the theft contributed to the story.
"There was a Picasso that was stolen and the theft increased the value because it added to the colour of the work's story.
"That is not usually the case though."
Many works were rolled up, treated badly and stored in conditions vastly different to the temperature controlled environments of museums and galleries.
"They are stored under beds, hidden away because they are that hard to sell," he said.
"I had a $6m painting handed to me in a garbage bag out the window of a Mercedes."
New Zealand art expert Penelope Jackson echoed Marinello's thoughts and concerns on the Lindauers' theft.
She said there was a lot of speculation as to motive but said until the culprits were caught it was largely an unknown.
"We just have to hope they are recovered unscathed because at 130 years old these two pieces are very vulnerable."
Jackson said talk that the gallery should not have had art in the window was a shame.
"It would be a sad thing if we got to the stage where galleries can't display art because there is a risk of theft.
"It's hard to entice people into an auction with blank walls."
Police put alerts on New Zealand boarders after the theft and Interpol was notified. Police continue to investigate.
Most art stolen within New Zealand has been recovered.
The most famous piece still "at large" is Psyche - a 1902 work by British artist Solomon Joseph Solomon.
In her book art thieves, fakers & fraudsters - the New Zealand author Penelope Jackson outlines the mystery of the 1942 theft.
Theories include an inside job and a phoney burglary to cover up damage done by a cleaner.
Hopes were raised in 1982 when a man came forward and said he had seen the life-size reclining nude painting in a Napier house.
It ended up being a similar painting by a Christchurch art student.
Later in the year the gallery received a Polaroid of what was thought to be Psyche.
The photo was later revealed to be a hoax with the clever confession:
Psyches sleep, Psyches awake
Some are real, some are fake
Masterpieces are seldom met,
Touch this one, the paint is still wet.
Other recovered high-profile pieces include the 1997 theft of Colin McCahon's Urewera mural stolen from a Department of Conservation visitor centre by Tuhoe activist Te Kaha. The work was returned 15 months later after negotiations.
In 1998 the $8m James Tissot oil painting - Still on Top - was stolen by career criminal Ricardo Sannd, also known as Ricardo Romanov.
Armed with a gun Sannd stole the painting, worth $8m, from Auckland Art Gallery. It was later found hidden under his bed.
Sannd was sentenced to nearly 14 years in prison for the crime.
In 2005 the statue Pania of the Reef was stolen from the Napier foreshore. The motive was never known but Pania was discovered a month later and recovered by police. She was restored, then replaced.