National Grid is battling in London's high court for access to secret documents relating to its £235m cartel case against a group of Europe's top engineering companies.
The case, which was launched in 2008, came after the European commission levied a €750m (£675m) fine on Switzerland's ABB, Germany's Siemens and both Alstom and Areva of France for participating in an "illegal cartel" that lasted for 16 years between 1988 and 2004.
The complaint revolves around the companies' sales of gas-insulated switchgear – industrial equipment used as a major component in electrical substations. According to legal documents, National Grid alleges that it suffered "substantial losses by reason of overcharges resulting from the illegal cartel".
The British company is now seeking access to confidential pleadings made by ABB, Areva, and Siemens in "leniency applications", which were made when the engineering companies were attempting to avoid the commission's fines.
The leniency policy allows immunity for prosecuted firms that inform the commission of a cartel's existence. ABB was exempted, while Areva and Siemens – which has just beaten Bombardier to the £3bn Thameslink train contract – "applied for leniency from the commission but their applications were unsuccessful".
Mr Justice Roth is now ruling on whether those leniency documents can be disclosed. Further evidence was also withheld by Alstom and Areva as the defendants claimed that French law prevented their release. These documents, however, were also held by Siemens and ABB and in a judgment ordering their disclosure by the non-French firms, Roth wrote: "There is no dispute that the documents of which disclosure is sought by [National Grid] are relevant to these proceedings and are documents to which [National Grid] would be entitled by way of standard disclosure under English rules in the absence of some supervening provision of EU law."
Regulatory fines of supplier cartels should make it easier for companies to prove wrongdoing in follow-up damages claims but some firms have been deterred from taking legal action because they fear they will reap only modest awards while destroying key business relationships.
National Grid, which is in the FTSE 100 and had revenues of £14bn last year, has previously insisted that it continues to enjoy good commercial dealings with the companies it is suing and looked forward to "engaging with them constructively throughout this legal process".
After the UK electricity industry was privatised in 1990, National Grid, which delivers gas and electricity across the country, was owned by 12 regional electricity companies and then listed on the London Stock Exchange in 1995. In the UK it runs the systems deliversing gas and electricity across the country. In the north-eastern US, it also provides power directly to homes.
A spokesman for Siemens said: "Siemens is fully co-operating with London high court's disclosure proceedings according to UK civil procedural rules."
National Grid, ABB, Alstom and Areva made no comment.