Every writer aims to make every work a masterpiece, but some are cursed by making only one, which outshines all the others as Saturn outshines its moons. Think of F Scott Fitzgerald and The Great Gatsby; of JD Salinger and The Catcher in the Rye; of Aidan Higgins and Langrishe, Go Down. In A Disused Shed in Co Wexford, Derek Mahon wrote the greatest single Irish poem since the death of Yeats, but his work, previous and subsequent, somehow escaped the glare of it.

But what a glare it is. The late Michael Longley told of how, one morning in the middle of the 1970s, he and his wife, the literary critic and academic Edna Longley, were having a weekend lie-in. Hearing the rattle of the letterbox, he went down to the hall and collected the post and brought it back to bed. One of the envelopes, on which he recognised the handwriting, contained a poem. He read it, read it again, then sighed grimly and said, “I’m giving up poetry.”

He didn’t, of course, for which we must offer thanks to the muse Calliope, but his impulse that morning is understandable. The poem was, of course, A Disused Shed, fresh from the smelter, its plangent power immediately apparent. It had its origins in passages from two novels, Troubles and The Lung, by his friend JG Farrell, in both of which there occurs the image of a tumbledown garden shed and “pale fungus growing towards the light”. In Mahon’s poems this becomes:

in a disused shed in Co Wexford,

among the bathtubs and the washbasins

a thousand mushrooms crowd to a keyhole.

...

They’re begging us, you see, in their wordless way,

to do something, to speak on their behalf

or at least not to close the door again.

Lost people of Treblin