The UK Financial Conduct Authority has intervened in a lawsuit against Royal Bank of Scotland regarding a claim that the bank mis-sold an interest-rate swap to two businessmen. The regulator is concerned about evidence presented by RBS. The FCA also says an analysis by a lower-court judge is "somewhat opaque". RBS has rejected the regulator's concerns, saying the judge had complied with FCA rules and had not misinterpreted the law. The "judge found that the appellants understood every feature of the swap about which they complained. Put simply, the swap was not mis-sold", according to RBS.