For those unfamiliar with Opeth, it's a tricky to endeavour to explain.

The Scandinavian five-piece have waltzed the line of death and progressive metal for nearly 30 years now, but that simplistic assessment doesn't do credit to the unique sound they have created.

Fusing those aforementioned elements with classic prog rock flourishes a la King Crimson, with the kind of dark folk musings Nick Drake shined briefly with, the band are an extraordinary contradiction of genres - often entirely within one song.

The thunderous rumbling of a barrage of drum blasts can segue into lilting melodies plucked carefully from the strings of a melancholy folk ramble.

You could be on a mellow walk through a Swedish forest or in the midst of a cacophony of noise from the apocalypse, and the chances are the song would be the same.

So with such an extraordinarily unique sound, both beautiful and fearsome at the same time, it's remarkable that Opeth have forged the kind of career they have where gigs at a venue like Norwich UEA are even possible.

It's not like the heady 1970s peak of prog where Yes and Emerson, Lake and Palmer were among the biggest bands on the globe, and the fact that Opeth have played the likes of the Royal Albert Hall and are fixtures at festivals like Download, show how hard they have worked given that they ply their trade with the kind of self-indulgent wizardry that doesn't bother the charts much.

But with 13th studio record In Cauda Venenum newly released, the band show no signs of slowing down on the boundary pushing prog which has gained them such a loyal following.

Sunday night's Norwich gig marks the start of the tour, which means debut performances of material from the new album nestled among obscurities and, if such a thing is possible for a band which most have never heard of, classics.

Frontman Mikael Akerfeldt is ever the self-deprecating talisman, answering audience heckles like he's having a chat in the middle of the street (shoppers in the market incidently may have witnessed him purchasing a leather shoulder bag earlier in the day).

Some initial nerves on the new material give way to a fine two hour medley of dark, doom-laden riffery, and although some of the big tunes are missing - The Grand Conjuration and Cusp Of Eternity spring to mind - the chance to hear rarities like Moon Above, Sun Below and big hitters like The Lotus Eater make for a unique foray into the dark underworld of Opeth's musical mastery.

Akerfeldt, Fredrik Akesson and Martin Mendez wield their axes deftly while the nuanced rooting of Martin Axenrot's drums and the mellotron-infused flourishes of keyboard man Joakim Svalberg make for a mesmerising display.

Adding to the musical finery for the first time is a stage much more busily furnished thanks to a couple of hefty plinths for the rhythm section and a superb light show which Norfolk's favourite son Alan Partridge might call a scaled down Pink Floyd show.

Whether its the hellish flames, quiet forest landscape or interstellar delights on the video screens or the stripped back lightbulb glow at the front of the stage, there is no denying the visuals add to the mood conjured by Opeth's music.

And while happy to be the guinea pigs for the new material and a refresh of the old, the Norwich crowd prove conclusively that they are ready to welcome Opeth back at any time.