Yet it seems the tale is even more extraordinary than we thought.
For yesterday it was revealed that the eccentric 79-year-old who guarded the paintings claims to know the whereabouts of a priceless piece of missing art dubbed ‘the Eighth Wonder of the World’.
Cornelius Gurlitt is said to have told his family he knows what became of the long-lost Amber Room, installed by Peter the Great in the Summer Palace outside St Petersburg in the 18th century.
Missing: The pensioner who was guarding a £1billion hoard of Nazi confiscated paintings in his flat claims to know the whereabouts of the Amber Room. A recreation of the room at Catherine Palace in St Petersburg is pictured
Grand: The room, which went missing during World War Two is thought to be one of the world's most valuable pieces of art
Wreck: A photograph of the original Amber Room in the Palace of Catherine The Great in St Petersburg after it was plundered by the Nazis
Speaking exclusively to the Mail from his home in Barcelona, Cornelius’s cousin Ekkeheart Gurlitt, 65, said: ‘He has always said: “I can tell you where the Amber Room is.”
'He has told us this all his life — “before I die, I will tell the public where it is, but not before”.’
If the claim is true, then it will shock the art world even more profoundly than the announcement of the discovery of some 1,500 artworks in Cornelius Gurlitt’s flat — whose existence was revealed this week, two years after they were discovered by German authorities during a tax investigation.
Although it is widely believed the panels were destroyed in a fire at Konigsberg Castle in April 1945, there has never been any definitive proof of this.
Over the decades, there have been countless investigations into the whereabouts of the room. One of the most outstanding pieces of art ever created, today it would easily be worth more than £200 million.
Ruins: The whereabouts of the Amber Room have remained a mystery since the original was stripped and left in this state by the Nazis
Designed by sculptor Andreas Schlüter, it was started in 1701, and originally installed in Charlottenburg Palace, home of the kings of Prussia.
But during a state visit, the room caught the eye of Peter the Great.
The Prussian monarch, Frederick William I, keen to cement a union with Russia, decided to donate the room to the Russian Tsar.
It was moved to the Winter House in St Petersburg, then installed at the Summer Palace in 1755.
After some renovations, it remained undisturbed until the Nazis invaded the Soviet Union in 1941.
Despite the best attempt by the Russians to hide the exquisite panels behind flimsy wallpaper, the Germans soon found the Amber Room, and tore it down within just 36 hours, before shipping it to Konigsberg Castle on Germany’s Baltic coast, where it is said to have met its fate.
Now, we are faced with the tantalising prospect of the continued existence of one of the world’s most wonderful treasures.
As the owner of his own impressive — albeit secret — art collection, and with a father, Hildebrand Gurlitt, who acted for the Third Reich as an art dealer, it is entirely plausible that Cornelius might know what became of it.
Yesterday, many more details emerged about the mysterious Mr Gurlitt, who is missing. However, Ekkeheart, a photographer, would not reveal if he knew if he was still alive.
Stash: The owner's name is written on a small plate at the house of German art collector Cornelius Gurlitt in Salzburg, Austria. An art collection worth some £1billion was reportedly found at his flat
‘I cannot tell you whether he is or not,’ he said. ‘It may be dangerous for him. If the police know he is alive, then they will come after him.
‘He has kept everything so secret for so many years. Now we don’t want to put him in danger. We don’t want any gangsters or “art mafia” chasing him.’
Incredibly, it appears the Gurlitt family has long known about their relative’s clandestine collection.
‘Of course we knew about it,’ admitted Mr Gurlitt.
‘But we kept it secret. We are not animals hungry for money. We do not want to sell our souls for 50 bucks. We are not greedy — we do not want to send him to hell. He has done nothing to us.’
Original home: The room was initially installed at the Charlottenburg Palace in Berlin once the home of Prussian kings, before being gifted to Russia
Mr Gurlitt also revealed that his own father, Dr Dietrich Gurlitt, 94, a retired geologist for the firm Gulf Oil, who now lives in southern Germany, near Lake Constance, had kept in contact with Cornelius, but he would not be drawn as to whether any contact had taken place over the past two years.
‘My father would wish him Merry Christmas, and a happy New Year, but there was no intensive connection,’ said Mr Gurlitt.
Nevertheless, Mr Gurlitt yesterday admitted that his father has been given some pieces of art by Cornelius. ‘My father knows nothing about art,’ he said.
‘I said to my father, “Look in [your] house! Maybe I will never have to work any more!” ’
Family secrets: Cornelius¿s cousin Ekkeheart Gurlitt, 65, spoke exclusively to The Mail from his home in Barcelona
Mr Gurlitt does, however, admit that the family is ashamed of the provenance of the art, much of which was bought at knock-down prices by Cornelius’s father Hildebrand from Jews fleeing Germany.
‘We are not proud of what our family did. These paintings are dirty money. They were stolen by the Nazis.’
Disturbingly, according to Mr Gurlitt, strange stories had long circulated in the family about Cornelius.
‘I’ve been told he’s a pederast,’ says Mr Gurlitt. ‘My father is a doctor, and he didn’t want us to have contact with strange people with abnormal sexuality.
'We heard strange stories when we were kids. We therefore didn’t have any intense connection [with Cornelius]. We knew he was a little odd.’
It is impossible to know whether the stories are true, but Mr Gurlitt says Cornelius, whom he has not seen for 30 years, is ‘very strange’.
‘He’s a little grey man,’ he says. ‘He was always perfectly dressed like an English gentleman. But he’s mentally in a mess.
'He’s a very poor sort. For 30 years, he has never let anybody in his apartment.’
Mr Gurlitt says that he too never set foot in the flat in Munich where £1 billion of art was discovered behind piles of rotting food, and where Cornelius is supposed to have lived for half a century.
This week, it also emerged that the reclusive German has a dilapidated second home which blights an exclusive Austrian suburb.
Yesterday, neighbours described Cornelius as being like a ‘phantom’ who has not been seen at the property — which he has owned for decades — for two years.
Intriguingly, that would coincide roughly with the point at which his art hoard in Munich was discovered.
Find: Around 1,500 paintings confiscated by the Nazis during World War Two were found at Cornelius Gurlitt's flat, pictured
Several locals told the Mail on Wednesday that they fear he may be dead inside the house, and want the police to search the premises.
Others believe the place may contain a second secret stash of paintings looted from the Nazis and worth millions of pounds.
The affluent suburb of Aigen in the south of Salzburg boasts Franz Beckenbauer, the former captain of the national football team, as a resident, and Cornelius’s house is a few hundred yards from the former home of the Von Trapp family, who inspired The Sound Of Music.
Art haul: The room was plundered by Adolf Hitler's Nazis during the Second World War
But the property has fallen into disrepair. Neighbours said he treated the home like ‘bunker’, and — despite the staggering value of the art stored at his home in Munich — was only ever seen driving an old black VW Beetle or scuttling from the car to his front door.
Helmut Ludescher, a long-term resident of the street, said Cornelius had been there for about 50 years, but he spoke to him only once.
He said: ‘He was like a phantom. The only time you ever saw him was when he was driving by in his car, and he didn’t even look left or right. He had a really pale face. We had almost no contact with him.’
Mr Ludescher continued: ‘Three years ago, I asked him if he was the owner of this house, and he was really grumpy and said “I won’t give you an answer”, got in his car and drove off.
‘He was very sullen and withdrawn. I have never once seen any visitors or friends at the house. I’m surprised they haven’t searched it. Maybe there are some more paintings hidden inside.’
Several neighbours believed Cornelius was a painter, but the only movement they saw in his house was a ‘ghostly’ light in the attic.
Police were called to the property in 2010 because of fears from neighbours that he might be dead.
Yesterday, another neighbour said those fears had returned following the dramatic recent revelations.
She said: ‘We want a search made. It is possible his body could be in there. When he was here he would keep himself inside as if he had something he wanted to hide.’
As for Cornelius Gurlitt’s family, they are remaining tight-lipped about his fate. His cousin, Ekkeheart, told me yesterday: ‘I think he is the most private art collector in the world.
Valuable: A reproduction of a painting by German painter Franz Marcthat was found in Gurlitt's apartment
'He told people that his father’s collection was destroyed by the Nazis, so that he could have peace for the rest of his life.
‘Maybe he has now committed suicide because he has no money.’
If that is indeed the case, he has left behind one of the most extra-ordinary mysteries of recent times — for surely the story of what became of the Amber Room would have died with him.
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Found: A painting by German artist Max Liebermann 'Zwei Reiter am Strande' (Two Horsemen at the Beach) was also found at Gurlitt's apartment