There’s something of a victory lap atmosphere inside London’s Royal Opera House, for this reprise of the Pet Shop Boys’ Inner Sanctum shows. Just as they did two years ago, the duo – now approaching their fourth decade of applying high-art concepts to pure pop exuberance – have taken up residence for four nights, possibly to facilitate a future DVD release (the final two shows will be filmed by regular collaborator David Barnard). While those 2016 shows marked the start of the Super tour, in support of the high-NRG, house-inflected album of the same name, there’s a feeling of familiarity about tonight.

There’s also sweat, buckets of it. As the deep red curtain, gilded in gold, ascends to reveal the first layer of designer Es Devlin’s eye-popping, multi-faceted set, the heatwave creeps in, temperature raised by dancing bodies, from the moment Chris Lowe triggers opener Inner Sanctum’s buoyant synth riff. “I thought this building was air conditioned!” Neil Tennant huffs later from inside a very unseasonal cropped bomber jacket after a suitably tropical Se A Vida É (That’s The Way Life Is).

A unique frontman, Tennant strides around like a pop evangelist, arms raised to the sky as he punctuates the chorus of Opportunities (Let’s Make Lots of Money) to almost football chant-esque shouts of “Go on Neil!” He’ll later reciprocate with a teacherly “that’s very good” after some crowd participation at the end of Domino Dancing. During a dreamy Home and Dry – accompanied by a retina-bursting prism of lasers – he sidles up to a keyboard and dashes off a one-finger riff with all the enthusiasm of someone emptying their junk folder. It’s oddly captivating.

Facebook Twitter Pinterest From last year’s Opera House shows, the Pet Shop Boys make their entrance. Photograph: Ken McKay

Lifelong fans of theatre, Tennant and Lowe also understand that they’re part of a bigger story. Having crafted stadium-sized shows for the likes of Beyoncé and Adele, Devlin knows how to manipulate space. During the opening section, after the pair arrive on stage wearing what look like upside-down colanders, Devlin keeps the circular motif going, creating overlapping spheres and vortexes with pin-sharp lasers. Steadily, each backdrop screen is lifted, playing with the audience’s depth perception. Songs are embellished by Devlin’s various visual constructs too; a large projection of Tenant’s face distorts and fractures as the gloomy The Dictator Decides starts to disintegrate, while the circular laser projections eventually give way to a series of concentric circles that oscillate menacingly during It’s a Sin.

Having made a career of balancing pop and art (see 2003’s greatest hits collection, PopArt), but fully aware that neither is mutually exclusive, there’s fun to be had within the high-concept framework. Introducing Left to My Own Devices, Tennant is joined by about 30 dancers each wearing a multicoloured inflatable suit. Their constant bobbing is mirrored by a backdrop of giant balloons, all tethered to the wall. The blur of various different blobs continues for the gloriously OTT Go West, which Tennant introduces with a typically wry bon mot: “We’re going to do another old song but in a new version. But which old song? There are so many to choose from.”

The set ends with a reprise of Super’s throbbing lead single The Pop Kids, a song that acts as both a potted history of the band and its continued mission statement. “We were young but we imagined we were so sophisticated,” sings Tennant, “Telling everyone we knew that rock was overrated.” In 2018, with poptimism at its peak, Tennant and Lowe may not need to keep fighting for pop’s critical legitimacy but thank God they’re still around to prove it anyway.