Thanks to "Game of Thrones," television just can't get enough of the Middle Ages. Those flickering smoky interiors, enormous woolly coats and bloody, ax-heavy battles; the remarkable décolletage, the picaresque foliage and mud. Sometimes there's magic, sometimes there isn't, but, by gosh, there's always plenty of bloody hacking and mud. Certainly "The Last Kingdom," the BBC drama that premieres Saturday and is based on the first book of Bernard Cornwell's "Saxon Tales," checks all these boxes in short order. Don't let the exposition-heavy first episode fool you; this may be a sword 'n' longboat epic with a handsome hero at...