Energy company Vattenfall faces a mass claim from customers after a court ruled it had unfairly raised its tariffs when gas prices increased sharply following the Russian invasion of Ukraine. The company put up its variable rates in April 2022 in response to rapidly inflating prices on the international gas markets, which quadrupled between January and August. But the appeal court in Amsterdam said Vattenfall’s decision to hike prices in April was an “unfair trading practice” because the conditions of...