The defendants are a number of UK and Japanese banks, including Mizuho, Mitsubishi, Sumitomo Mitsui, Bank of Yokohoma, JPMorgan Chase, Barclays, HSBC, and so on. The plaintiffs allege that the defendants manipulate the Euro-Yen LIBOR rates. The defendants objected to the plaintiffs document request, claiming that the request violated UK's Data Protection Act and English Common Law duty of confidentiality for bankers.
The magistrate found that a UK court could plausibly find the defendants violated the DPA and duty of confidentiality. After the Aerospatiale comity analysis, the court overruled the defendants' objection.
Geoffrey Sant reported that there is an alarming increase in U.S. court order to violate foreign laws, especially in the context of discovery and bank secrecy. See Geoffrey Sant, Court-Ordered Law Breaking: U.S. Courts Increasingly Order the Violation of Foreign Law, 81 Brooklyn L. Rev. 181 (2015). This is another iteration of such court-ordered law breaking. Magistrate Pitman found that a UK court could find that the defendants violated UK laws, but ordered the defendants to produce the documents at any rate.
An interesting side point is that even the Japanese banks can plausibly seek the protection of UK's data privacy laws--attesting to the ethereal nature of personal data that nonetheless gives rise to a territorial "hook."