Throughout his time at Eton, Shelley saw much of Tom Medwin during vacations. During the winter of 1809-10, the cousin, who would soon go to Oxford, and the cousin, who would soon leave it for the army, were inseparable companions. During their long walks through the leafless glades of St. Leonard's Forest--in the clear frosty air and under the bright skies, that had a most exhilarating effect on their spirits--these two young men of common blood and kindred tastes discoursed with more enjoyment than discretion on the principles of poetry and romantic prose, of ancient science and modern culture. This was the winter, when they set to work on the production of a wild story (with a hideous witch for its principal character), that seems to have justified its title of _Nightmare_, before they ceased writing alternate chapters of the morbid tale, and threw themselves with greater enthusiasm into the much higher and more arduous enterprise of a grand 'metrical romance on the subject of the _Wandering Jew_,'--an enterprise in which the two cousins were encouraged and influenced (though not actuated from the commencement) by one of those accidents, which so often influence, and sometimes determine, the course of human genius.
On his way through Lincoln's Inn Fields, Tom Medwin picked up at a bookstall the following passage, from a free English rendering and adaptation (with variations from the original) of Christian D. F. Schubart's rhapsodical poem _Der Ewige Jude_.
'Ahasuerus the Jew crept forth from the dark cave of Mount Carmel. Near two thousand years have elapsed since he was first goaded by never-ending restlessness to rove the globe from pole to pole. When our Lord was wearied with the burden of his ponderous cross, and wanted to rest before the door of Ahasuerus, the unfeeling wretch drove him away with brutality. The Saviour of mankind staggered, sinking under the heavy load, but uttered no complaint. An angel of death appeared before Ahasuerus, and exclaimed indignantly, "Barbarian! thou hast denied rest to the Son of Man; be it denied thee also, until He comes to judge the world!"
'A black demon, let loose from hell upon Ahasuerus, goads him now from country to country; he is denied the consolation which death affords, and precluded from the rest of the peaceful grave.