President Volodymyr Zelensky of Ukraine arrived on Sunday afternoon in London for talks with the leaders of Britain, Germany and France as Europe considers taking a more active role in peace talks with Russia after more than a year of unsuccessful U.S. mediation. Ukraine and its European allies see a new opening to revive talks that have stalled as Moscow made uncompromising territorial demands and Washington shifted its focus to the war with Iran. They note that Russia’s recent battlefield setbacks and mounting economic strains could make a peace settlement more appealing to the Kremlin, a scenario that is also...