Right, which presumably means that the tale originated before the Saxons invaded Great Britain. But nonetheless the version we know is told in Old English and

Right, which presumably means that the tale originated before the Saxons invaded Great Britain. But nonetheless the version we know is told in Old English and not any of its continental predecessors, and its earliest manuscripts are all found in Britain. It isn't disqualified from being uniquely English by the fact that it derives from earlier times in Scandinavia any more than Mormonism is disqualified from being uniquely American by the fact that it derives from earlier times in Jerusalem.