Original sentence: At thirteen he went to Gresham's School in Norfolk, where, in 1922, when his friend Robert Medley asked him if he wrote poetry, he suddenly realized that his vocation was to be a poet; he had not written any poems before he had this realization
Edited sentence: At thirteen he went to Gresham's School in Norfolk, where, in 1922, his friend Robert Medley asked him if he wrote poetry, Auden realized his vocation was to be a poet