The latest British tailored-clothing brand to break out of its traditional uniform with contemporary sportswear and suits is E. Tautz. Established in 1867 in London’s prosperous West End, the historic brand—which in its heyday supplied bespoke sporting and military apparel for luminaries such as Winston Churchill—is opening a London flagship store on Duke Street in the Mayfair neighborhood in September. The brand joins a lineup of time-honored British brands that use Savile Row–grade tailoring skills and luxur…