Photo by Agata Urbaniak

Agit-provocateurs Laibach made headlines around the world last year when they became the first major Western rock (in the loosest possible sense of both terms) band to play concerts in Pyongyang, as part of the celebrations of the seventieth anniversary of North Korea's liberation from Japanese occupation. What was even more delicious than the idea of expert ironists who grew up under totalitarianism in Yugoslavia being invited to play before the assembled apparatchiks of the North Korean elite, was the notion that they would perform not only their own most recent - and very much pop-influenced - album Spectre plus a sprinkling of greatest cover version hits, but also - ever fond of appropriating pop culture for their own ends - their very own take on songs from The Sound Of Music.

Now, Laibach bring their Pyongyang-honed musical theatrics to London, and while there might not be rows of uniformed state functionaries in bemused attendance tonight, there's still plenty of military-surplus fashion on display among the black-clad industrialists in the crowd, and worn by the band for that matter. It's also entirely fitting that The Forum's architecture has a decidedly Roman bent, with its Art Deco motifs and martial frescoes – the latter allegedly funded by Mussolini in honour of a rally in Kentish Town by Oswald Moseley's British Union of Fascists that seems not to have actually happened - just as the secretive financing probably never did either.

Apocryphal or not, that's just the sort of rumour, innuendo and circumstance that Laibach thrive on, especially given their 35 years of exploring the relationship between rock concerts and political rallies. This intricate relationship with politics and entertainment has been found in moments such as when they were the only outside band to play during the siege of Sarajevo during the Occupied Europe NATO Tour in 1995 - a provocation that lead to Laibach's hotel being car-bombed when they played in Serbia in 1997 – up to the spectacular Retro Monumental Avant-Garde concert in the Turbine Hall of the Tate Modern.

Their penchant for performing painted entirely gold, bracketed by floor to ceiling black banners emblazoned with their cross and cog emblem deliberately evoked - and mocked - a decidedly dubious aesthetic. Tonight, the decorations are restricted to a complex flow of imagery and sloganeering on screens and the sort of eyeball-frying lightshow which fairly bellows that contemporary stadium bombast is firmly part of their canon of self-referential targets and tropes to be pushed to the limits.

Ever in control of their image and sound, Laibach keep the crowd entertained for half an hour of music from The Sound Of Music before their eventual entrance to an atonal roil of squirming synths and rolling drums. We are not in the apparently familiar Alps as rendered by Hollywood and Broadway now, but are entering into Laibach's very particular and ambiguous vision of a psychic landscape as seen from a Slovenian perspective, not far from the musical's setting in Austria.

Pushing the boundaries of pop as much as of the idea of Europe, tweaking the parameters of the stadium rock paraphernalia - synchronised lyrics and images on the screens, hard sell on the merchandise stall, full-spectrum branding of everything with Laibach's immediately identifiable canon of industrial and political signifiers - they have the moves and the methods perfected, but always with that edge, that challenging self-awareness that the audience enters into at their behest and with gusto.

Not a superfluous word is spoken on stage by either Milan Fras or Mina Špiler throughout, all the banter stripped back to a mocking speech synthesizer with a heavy Central European tone: "Hello Europe" it says in welcome, "Make some noise; make some fucking noise", or "Take a break now to chill out", when the interval countdowns tick across the screens.

Every song choice seems like a socio-political comment (because it undoubtedly is) - when Laibach break out the stark 'Eurovision', it seems especially appropriate in a Britain obsessed with the prospect of Brexit with its proclamation that "Europe is falling apart" - and the projected jackboots over 'Walk With Me' hardly need further explanation. 'No History' marks the moment where Taylor Swift meets Francis Fukuyama, and 'Anglia' continues the tradition of fitting in a sardonic cover of their host country's national anthem into the set.

Following a short intermission with waltzes played over the PA, the robot voice announces: "Now for something completely different". Cue projections of (presumably) North Korean schoolchildren playing piano that introduces an astonishing take on 'Do-Re-Mi'. The audience take up the refrain just as the industrial beats kick in and a vocoded whirr takes up the song, and Fras is at his most guttural while Špiler gets to stretch her vocal range once again.

Tonight we get 'Edelweiss' reimagined as a power rock ballad in an inimitable Laibach style and 'Climb Every Mountain' belted out like it was a Nietzschean imperative. 'The Sound Of Music' itself is so industrially symphonic that Rodgers and Hammerstein must be rotating at a steady 120bpm in their graves - the average schläger oompah fest has nothing on this for both bombast and good-time singalong fun either, leavened with the ever-present cynicism that never actually falls into kitsch for its own sake.

Watching Laibach play live, it so often feels like they have quantified and distilled the form that all rock and roll bands aspire to into its essential nature: uplifting, disturbing and powerful. Tonight, as ever, Laibach prod at the latent respect for totalitarian authority among the crowd, the storming, stomping encore of 'Life Is Life' transforming into the still-more aggressive German-language version 'Leben Heisst Leben' with all the disturbing collective stomping zeal of both the Nuremburg Rally and a Queen arena gig. The night ends in an enthusiastic breakdown into slo-mo clapalong that brings everything back to a state of willing participation under one band's rigid direction - for better or worse.