An untold amount of Greek heritage has been lost to international smugglers, but now Greece is fighting back, determined to bring its treasures home.
"Smuggling is a very big problem and it is becoming bigger by the day. Everybody in Greece is doing some kind of digging or looting somewhere."
Greece is littered with antiquities and archaeological sites
Yannis - the name he gives himself - is a key figure in the international smuggling network.
In an exclusive interview for BBC Radio 4's Crossing Continents, conducted at a secret location, he revealed his insights.
"It starts at the top, from politicians down to ordinary people," he continued, "and the motivation is always money."
"Everyone knows it's illegal. There's dirt on all layers of Greek society. I repeat: A lot of dirt!"
The programme met another man who operates incognito but for the opposite reason - to catch the thieves.
He is Major Yiorgos Gligoris, head of the Art Crime Squad of the Greek police, and he is leading the current crackdown.
"Smuggling is a really big problem in Greece and dates back centuries. There are illegal digs still going on all over Greece," he said.
"People are not well-off today. This is an alternative way of making money. It's the same in Turkey, South America, Egypt and Italy, countries where there are lots of antiquities and lots of rural poverty.
"We are the 'source countries' supplying to the 'consumer countries' like the US and the UK."
Greece has at least 3,000 museums and open-air archaeological sites, and about 20,000 shipwrecks.
Protecting the huge number of sites and antiquities is difficult
Protecting the antiquities and stopping the looters has always been difficult.
Greek laws governing the ownership of antiquities are in fact very strict: everything you find on Greek soil belongs to the state and must be registered.
There's also the 1970 Unesco Convention on Cultural Property, which supports international co-operation on ownership.
But in both cases the problem has been enforcement.
Two recent scandals have focused Greek minds on protecting their property and on pursuing the looters.
In spring this year, Gligoris and his team raided the Cycladic island homes of the American Marion True, a former antiquities curator at the J Paul Getty Museum in Los Angeles, and the home of the late shipping magnate Christos Mihailidis.
This programme was first broadcast on Thursday, 3 August 2006, at 1102 BST
Over 300 objects in total, allegedly unregistered, were seized and are being investigated.
Ms True is currently on trial in Rome for allegedly conspiring to receive stolen antiquities for the Getty Museum.
She denies all wrong-doing.
Whatever the verdict, this is the first international trial of its kind in the trafficking of illegal antiquities.
Yannis, the middleman turned police informer, told the programme how the network operates.
"The looter often knows the middleman so he may smuggle to order. The antiquities then go abroad - usually first to dealers in Switzerland and Germany. This happens by lorry and by boat," he said.
Some of the Cycladic figurines can fetch millions of Euros
"Thousands of trucks leave Greece every day and the objects are hidden in boxes and food, like watermelons."
He continued: "Some objects such as Cycladic figurines can fetch millions of Euros. They are among the most valuable antiquities in Greece today."
When asked whether he accepted responsibility for his crimes, Yannis replied:
"First of all, I am not a looter. I was a middleman. It's the state I blame and the many grey areas in the law.
"Even if an object is ultimately declared 'legal', and has been bought via a big auction house or dealer, it has often arrived there via illegal digs and dealing.
"Governments and museums all over the world are aware of this and often turn a blind eye.
"I can't name names but I know politicians who are involved either directly or indirectly in this trade.
Some of the world's biggest museums have not explained how they got their acquisitions
Yannis, former antiquities thief
"Some of the world's biggest museums have not explained how they got their acquisitions - so we have to assume that these objects have been smuggled," he said.
Greece is now putting pressure on museums and collectors to return disputed artefacts.
The international consequences of Greece's crackdown are huge.
In July, the Getty Museum promised to return two statues. It is expected that more museums will follow suit.
Success depends to a large extent on the police major, Yiorgos Gligoris, a man with a mission. How does he operate?
"As with police all over the world, we work with our sources. We get tip-offs," he said.
"Most of the time I pose as a buyer or dealer - which is why I work undercover and don't appear in public.
"I spent a long time studying Greek antiquities when I got this job. I have to know the prices on the market. I have to know how the looters think and act.
"They must believe in me. It's the way you dress, the car you drive, the places you go.
"You can't pretend to be a millionaire and take them to a small cafe for lunch. You have to take them somewhere posh. I have to be a good actor too."
However, when he was asked whether he had the resources and staff to support his campaign, the ebullient Gligoris was subdued.
"We have a total of 27 police [in the Art Crime Squad]," he said.
"It is not enough and there should be more. I'd like more police obviously, and more cars, a helicopter perhaps, and everything that modern technology provides.
"They have all that in Italy and it shows in their success.
"But combating this crime can't just be left up to the Greeks - no matter what measures one country takes this is an international crime."
Yannis agrees with Gligoris on several points: they both love Greek antiquities and think they should be returned to Greece.
"I regret what I did," said Yannis. "During my work I fell in love with the antiquities and that's why I stopped. They must not leave this country!
"The trade is really dangerous today and there are fewer dealers. The police are on their trail."
"But people are still digging," he concluded pessimistically.
BBC Radio 4's Crossing Continents was broadcast on Thursday, 3 August 2006, at 1102 BST and will be repeated on Monday, 7 August at 2030 BST.