The European Union announced this week a new round of economic sanctions targeting 100 Iranian companies, including Tehran's main European financial hub, the Hamburg-based European-Iranian trade bank (EIH).
British diplomats and nuclear proliferation experts played a key role in ratcheting up the pressure on Chancellor Angela Merkel's government to drop its resistance to blacklisting the EIH.
In March, British security experts provided evidence to the German Foreign Ministry in Berlin about EIH's questionable financial dealings.
In early April, the business daily Handelsblatt revealed that the German Foreign Ministry, through its top diplomat Guido Westerwelle, "rubber-stamped" 1.5 billion euros' worth of crude oil payments from India to Iran via the EIH.
The pro-business Foreign Minister Westerwelle catapulted Germany into an international scandal for effectively allowing funds to flow into Iran's nuclear and missile programmes.
Last year, the US Treasury Department sanctioned the EIH because it had played a part in advancing Iran's nuclear and rocket projects.
According to a WikiLeaks cable from as early as 2008, Will Gelling, the head of Foreign and Commonwealth Office Iran Co-ordination Group, noted that the UK "is pushing Germany on this bank with a view to an EU listing" but "Germans are pushing back".
A second 2008 British WikiLeaks dispatch conveys the frustration of trying to rope Germany into a robust sanctions strategy against Iran: German agreement on anything meaningful will be like "pulling teeth," reads the entry.
The UK's efforts to twist Germany's arm to shut down the EIH's operation have been mostly unreported. The Anglo-American analysis about the dangers of the so-called terror bank EIH was well ahead of the security curve. It appears that the Merkel administration prioritised short-term profits over long-term global security.
Nonetheless, the decision to ban EIH, largely because of its strategic importance in Iran's drive to go nuclear, might very well be the crowning achievement of this EU sanctions round.