In some ways Kae Tempest should come as no surprise: in a musical era when words spoken over beats are nothing new, when rapid-fire streams of consciousness stir and entertain at poetry slams, or when careworn solo voices have found a home in mainstream 21st-century music charts. Poetry for the damaged and defiant soul, as performance, has never been more fashionable, not since the beat poets rubbed turtle-necks with folkies and rock ‘n’ rollers in London or Greenwich Village, when Bob Dylan, Jim Morrison or Lou Reed, if forced, would choose ‘poet’ over ‘singer’. Since then we’ve had Gil Scott-Heron, John Cooper Clarke, Henry Rollins, The Streets, Nick Cave, Sleaford Mods, Ghostpoet…

But edge-iness cuts both ways – an artist who speaks words over electronic atmospheres and beats might have sounded a pioneering idea twenty years ago, but since rap, hip-hop, grime etc. became global hyper-selling phenomena, it needs someone special to assert not only an individual personality that sets itself above the genre, but to stamp authority and ownership: I, and my work, are different. A glance at the list of accolades won over the last twelve years substantiates the artistic seriousness of the artistry of this prolific south-London poet, rapper, playwright and novelist: see their* Ted Hughes award, New Generation Poet award (bestowed only once every ten years), and reliably fulsome critical reviews of albums and live shows (*two years ago, Tempest, formerly Kate, signalled publicly non-binary gender identity and employment of they/them as personal pronouns.)

Witnessing Kae’s Edinburgh International Festival visit to Leith Theatre, it’s clear from the off that you are invited on a very individual musical and lyrical journey that no-one else could take you on. There’s a maoist austerity to the schoolboy haircut and buttoned-up shirt with workwear trousers, and the opening few minutes of introduction are taken up with a warmly grateful testimony of how happily at-home the artist feels in Edinburgh, and not to expect any between-track chat as, with keyboardist Hinako Omori, they roll uninterrupted through the justly-acclaimed recent album The Line is a Curve, as on the recording. The performer-audience friendship thus fixed, Tempest has the enduring, heartfelt affection of the filled Leith Theatre.

But we get to hear plenty over the following hour-plus: astonishingly free of ‘cheat-sheet’ visual prompt, rarely letting-up or, seemingly, pausing for breath, a dense, never-ending flow of wordage proceeding from the artist’s mouth: vast in range from tender to explosive, from delicate to solid – detailed and often beautiful. The old expression about ‘swallowed a dictionary’ comes to mind as line after line flies out, with rhyme and shape constantly changing and evolving – highly descriptive of the outer world as much as inner feelings. Strong emotions, from relationships and introspection, sometimes locking-in with the chatter of insistent electronic beats, sometimes lying gracefully across them. Words as texture and melody as well as conveying meaning, restless then restful, expansive then introverted.

While sonically the repertoire is reproduced faithfully with all details present and correct, it’s nonetheless a revelation to witness it recited live, without audible stumbling: most of us who struggle to remember, nay recite, even a verse of Tam O’Shanter would be properly astonished at how Tempest can bring so much up, from so deep in the well, wandering left and right of stage, not merely regurgitating the words but delivering them, eye-to-eye, to the audience.

I hope most of them also appreciated, like I did, the shifting subtleties in the electronic landscape – and it is landscape I’d suggest, these aren’t really ‘songs’: the slightly-ragged percussion in Nothing to Prove, or the bubbling sequencer-chatter underpinning I Saw Light, which on the recording Kae shares vocally with Irish band Fontaines DC’s Grian Chatten. Then there’s the way the shimmering dance of More Pressure synchronises with the coloured spotlighting, or the ‘extra’ ninth beat in every bar of Firesmoke, delicious every time it comes round – one of several tracks from their three glorious previous albums, culminating in the lurching Circles.

After leaving the stage, Tempest returns, but merely to thank the audience: taking a principled stand on the ‘issue’ of encores, which they find ‘manipulative’ – it’s an authentically honest farewell from an ‘upfront’ artist and, the show thus delineated, no-one leaves disappointed.