Four years after one of the most dramatic acts of sabotage in modern European history, a Ukrainian man goes on trial in Hamburg on Wednesday accused of blowing up Russia's Nord Stream gas pipelines to Germany.
Serhii K, as he is identified by German prosecutors, is accused of plotting with other Ukrainian military personnel to destroy the pipelines and stop Russia financing its war with gas revenue.
The case is highly sensitive in Germany, seen as one of Ukraine's closest allies since Russia launched its full-scale invasion in February 2022, seven months before the attacks took place.
Serhii K, extradited to Germany last year, will become the first suspect to go on trial for the blasts.
He denies the charges, as does a second suspect who is fighting extradition from Croatia.
In the months after explosives destroyed three of the four gas pipelines in the Baltic Sea off the island of Bornholm on 26 September 2022, Western suspicion looked towards Moscow without directly apportioning blame.
Russia had already shut off the flow of gas to Germany in Nord Stream 1 weeks before the attack, and Nord Stream 2 had never been turned on. Berlin had frozen the multi-billion dollar project shortly before the invasion and there were reports of suspicious Russian naval movements before the blasts.
The case has highlighted differences of opinion on the trial in Kyiv and Berlin.
Oleksandr Merezhko, who chairs the Foreign Affairs Committee in the Ukrainian parliament, points out that the blasts took place during a time of war with Russia and "Nord Stream 2 was nothing but a tool used by Russia in order to get prepared for the war".
He told the BBC they had no confirmation of the German account: "It's one of the versions."
However, Stefan Meister, of the German Council on Foreign Relations, says successive chancellors in Berlin have done their best to remove the politics from the case.
"They tried to make not a big story out of it, not to give it too much attention, to give it to the institutions, to the judiciary that they will deal with it. This is not a political case. So they tried to depoliticise it," he explained.
In August 2025, Serhii K was arrested after checking into a hotel near the Italian Adriatic resort of Rimini, by police acting under a European arrest warrant issued by federal prosecutors in Germany.
After several weeks of court battles fighting extradition, Serhii K - identified in court documents as Serhii Kuznetsov - was transferred to Germany late last year.
German prosecutors allege that in 2022 he was a serving officer in the Ukrainian army, external, and he had led a group of professional divers, a boat captain and an explosives expert.
While his legal fight was going on in Italy, another Ukrainian man called Volodymyr Zhuravlov successfully challenged Germany's extradition bid in a Polish court.
In a ruling very different from Italy's Supreme Court, the Polish judge ordered Zhuravlov's release in October 2025, stating that the attack on the pipelines was not unlawful, and if Ukraine had organised an armed mission it was "justified, rational and just".
Although he was released by the court in Warsaw, he was arrested last August in Croatia on suspicion of being a suspect who "participated in the dives necessary" for the sabotage.
Last month, Croatia approved his extradition, although it is not clear when that will happen, and if his case could become part of the Hamburg trial.
Despite the difficult nature of the case for Kyiv and Berlin, Ukrainian MP Oleksandr Merezhko does not believe it will spoil relations as "it's in the best national interests of Germany to continue to support us".