The Svenska Dagbladet (SvD) newspaper on Tuesday revealed its findings after trawling through 15 boxes of material that the Swedish journalist compiled on his quest to solve the murder.
Much of the paperwork focused on Cyprus-based Swede Bertil Wedin, with documents stating that the suspected mercenary may have been in contact with South African security services in the run up to the murder of the fierce anti-apartheid critic Palme. SvD reported that Wedin had confessed four years before the murder in a British court case that he had been in touch with South African agent Craig Williamsson.
The bulk of the documents was handed to Larsson by the British publication Searchlight, which tracked rightwing movements. Larsson himself would go on to found the Expo Foundation, which to this day publishes an anti-racism magazine in Sweden. He would also go on to pen the Millennium trilogy about journalist Mikael Blomqvist and hacker Lisbeth Salander.
Larsson had shared some of his findings with the Swedish authorities, but his long-term partner Ewa Gabrielsson told SvD that Larsson had little respect for the Swedish security police after their initial meeting, dubbing them "idiots".
"He had to start the first interview with a lecture on the difference between Nazis and socialists," she recalled.
A year after the assassination, Larsson handed his notes over to the authorities. The "South African lead" would also eventually make headlines in Sweden. Yet the Swedish police has never questioned Wedin in the 28 years that have passed since the shooting in central Stockholm.
Swedish police professor and author Leif G.W. Persson on Tuesday commented the lapse in the investigation by telling SvD that the Swedish police were ill-equipped to deal with politically motivated murders.
"They can deal with old hoodlums, but as soon as they're stuck in a political context or have to go abroad, they're lost," Persson told SvD.
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Wedin himself, now 73, said he had nothing to lose from the truth being revealed as he was not the killer.
"I disliked Palme quite a lot but I did not hate him," Wedin told SvD in an exclusive interview. He denied being a mercenary and a South African agent. He said he had invited Swedish police to fly to Cyprus to speak with him about ten years after the murder when the Swedish media was reporting on the South African lead.
"A policeman called. He was a bit 'hello and hi' and talked about permits," Wedin recalled. "I told him he didn't need permits, that he should just come down. But they never came."