This discovery was quickly followed by another breakthrough. As Stensrud worked his way through 100-odd witness statements, he paused at the testimony of a Texan, who had told interviewers that he was certain the gun the robbers used was a Magnum .357, common in the US but rarely seen in Norway.
Police searched through all recorded gun crime looking for criminals who had used a .357. A few hours later they had a match - Petter Tharaldsen.
This was the same Petter Tharaldsen who had been dragged out of the water after stealing [pounds sterling] 500,000 from a money courier - and was still in custody. But Tharaldsen refused to talk, and his accomplice in that attack, Lars Harnes, gave him an alibi. He claimed they were together planning their cash heist at the time of the Scream raid.
While being questioned, Tharaldsen was offered some coffee in a paper cup.
In a move that was later to cause controversy, investigators took the cup and sent it for DNA testing in an effort to see whether it matched DNA recovered from the car used in the Munch robbery. It did - and further DNA evidence recovered from the getaway car linked the vehicle to a well-known car thief. Stensrud raided his apartment and arrested another three men. But, like Tharaldsen, none of them were prepared to talk about The Scream.
Stensrud was getting desperate. 'Time seemed to be running out,' he admitted.
Despite the arrests, nobody - not even the regular informers - would talk.
Police didn't have a clue where the paintings might be. The press, however, had no problem getting information from the criminal underworld and printed various headline stories, first that they had been irreparably damaged and then, to everyone's horror, that they had beenincinerated. 'I ignored these reports; we do not use newspapers as a reliable source here in Oslo,' said Stensrud dryly.
Instead, he focused on Tharaldsen, convinced he was the key to the location of the pictures. He checked on all of Tharaldsen's associates and came up with 30-year-old Stian Skjold.
A team of surveillance experts was scrambled to keep watch on him 24 hours a day. On September 24, 2004, they followed him to a farm where, incredibly, Stensrud's team spotted the second car used in the getaway from the Munch Museum. They watched as Skjold climbed on to a disused bus, reached under a seat and pulled out a rolled-up carpet. Inside was a plastic bin liner. He opened the bag, peered inside and lifted out the paintings. The police could hardly contain themselves.
While they decided on their next move, a second car drew up and parked out of view. Suddenly, the two cars sped off and split up. The surveillance officers were frantic. Which car were the paintings in? They decided to stick to their brief and followed Skjold. It was the wrong choice. The police had another man but they had lost the paintings. And to Stensrud's frustration their latest suspect also refused to talk.
Then, in April 2005, the break Stensrud needed finally came. Just as he had suspected, Toska, the head of the bank robbery, had used the diversion of The Scream to escape Norway for Malaga in Spain. But Malaga's police had been sent a copy of Toska's description and spotted him with a well-known drug dealer. On April 5, one year to the day after the vault robbery, armed police raided Toska's hotel room. Confronted with the evidence, Toska admitted taking part in the cash raid.
During his trial Toska ballooned; he consumed ingot-sized bars of chocolate during coffee breaks as he anxiously awaited the outcome. In March this year, he was found guilty and sentenced to 19 years in prison. Yet even in his cell Toska would not reveal what Stensrud suspected - that he had ordered the theft of the paintings.