Whatever prompted festival organisers to programme the first modern performance of a 16th-century Scottish epic poem, I doubt it was burning topicality. And yet here we are, in the midst of the firestorm about the meaning and purpose of punishment sparked off by the release of Abdul Baset Ali al-Megrahi. And here is Robert Henryson, 500 years ago, pondering much the same thing.

The story of Troilus and Cresseid — or Cressida, or Crisseyde, depending on the version —– usually ends with the young Trojan Troilus in despair at his beloved Cresseid’s betrayal of him with the Greek Diomede. But Henryson, specifically alluding to “worthy Chaucer”, who follows Troilus to his death, is determined to follow Cresseid to hers.

A relentlessly grim tale it is, too. Dumped by Diomede, she makes the mistake of complaining to the gods that it is all Cupid’s fault. A celestial star chamber is convened in which the gods inevitably take Cupid’s side and condemn her to leprosy (often associated with venereal disease at the time), penury and a wretched, lonely death.

To compound the agony, Troilus himself passes by the leper house, leaving generous alms. They do not recognise each other. Only after he has left do the other lepers tell her who it was. She consigns her body to the worms.

All this is told by an old man beside a bare tree on a wintry hillside. It is, as the poet says, a suitable place and season for such a tale, and David Levin’s austere production of Elizabeth Elliott’s supple translation makes few concessions, just as none are made to Cresseid.

If all this was just a cautionary tale about a faithless woman getting her come-uppance, I doubt the poem would have the currency it has (Seamus Heaney also translated it recently). But this is not so much a judgment on Cresseid but a judgment on those who condemned her. Did it change anything? Did it make Troilus happy? Jimmy Yuill as the poet, hair on end, can only shake his sagacious head wearily at the savagery of it all.

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