However much you might love the eclectic, unpredictable Fringe, there are times when we all crave a good solid piece of writing, and a performance that lets you know you’re in safe hands. Shylock is such a play. Returning to Edinburgh after a five-year absence, it’s written by much-starred actor (and Shakespearean scholar) Gareth Armstrong, but performed here by the equally well-regarded Guy Masterton – perhaps best known at the Fringe for his one-man adaptations of Under Milk Wood and Animal Farm.

As the title suggests, this is an exploration of Shakespeare’s Merchant of Venice, but the story isn’t actually told through Shylock’s eyes. Our narrator is a man called Tubal: a character who, unless you’re the most dedicated of Bardic buffs, you’ve probably never heard of before. He appears in exactly one scene, and is mentioned in precisely one other – but, as Armstrong’s Tubal is all too anxious to remind us, he’s Shylock’s one and only friend. Much humour is made of Tubal’s jealous claim to that status, but there’s a serious point here too; a reminder of how isolated Shylock’s life would have been when Jews in Venice were required to live behind locked gates, surrounded by high walls.

In Shakespeare’s England, mind you, things were even worse. The Jewish community had been expelled – and one of Armstrong’s most striking observations is that Shakespeare could never have met a Jew, at least not one who acknowledged their identity. To reinforce the point, Tubal illustrates how Jews were portrayed in theatre at the time, a grotesque parody made all the more chilling by the humorous relish with which Masterton performs it. It’s important context for interpreting the more problematic aspects of Shakespeare’s text; and there are other analytical strands as well, unpicking some of the implications and meanings that might pass a modern audience by.

Masterton is convincing and commanding as Tubal, yet he also brings an air of homely geniality to the role. It’s a combination that ensures the densely-packed script never feels too ponderous or lecturing. More sensitive or shocking moments stand out well amidst the general bonhomie, and he switches adeptly into other characters as the narrative demands, while always retaining enough of Tubal to remind us who’s telling this tale. It’s a sprightly performance too, bringing visual interest to a relatively bare stage – though three hanging banners, covered with the word “Jew” translated into dozens of languages, serve as a constant reminder of just what this play is all about.

Ultimately, Shylock is unashamedly educational, but it delivers its lessons with a lightness of touch and an ironic sense of comedy. The credit for that’s equally shared between Armstrong’s finely-tuned script and Masterton’s note-perfect performance – with results that are entertaining and informative, and deliver a warning too. Both a study of Shakespeare and a brief history of prejudice, it’s a meaty, thought-provoking, yet thoroughly enjoyable play.