The Competition Appeal Tribunal is tucked away on the seventh floor of an anonymous office block near London’s Fleet Street. Other than the lawyers working on their laptops in the grey-carpeted venue, there are hardly ever any other visitors.

This obscure little court was for years a backwater of London’s legal industry hearing important but somewhat arcane arguments over antitrust and mergers. But a change to the law in 2015 has catapulted this court into a multi-billion pound centre for consumer rights cases—all without the public really having any clue about it.