Immortally execrable ...

... Knight of the white elephant.

The realization that he was a great poet came to McGonagall in 1877 with the suddenness of a mystical experience or perhaps a neurological event like a stroke. (These days, he would be put at once into an MRI scanner.) From that time on, he ceased ever to work as a cotton-weaver, deriving an exiguous and precarious living from performances of his own compositions in places such as village halls, public meeting rooms, and pubs. His wife begged him to return to cotton-weaving, where the remuneration, while not munificent, was at least regular and more or less calculable in advance. But McGonagall was faithful to his muse to the last, dying in penury in 1902.