The Levellers, Royal Albert Hall, London

To celebrate the 20th anniversary of their formation, The Levellers have transformed the Royal Albert Hall into what appears to be a late-Eighties Greenpeace rally. Their fans (or the Merry Hitchers, as some prefer to be known) may be sat comparing nose-piercings and reminiscing over past protests for now, but the glazed glint in their eyes suggests that all are here to party like it's 1988.

For a band that have trademarked the phrase "Rolling Anarchy", the lavish 19th-century auditorium is an odd choice of venue, but this is a birthday party, after all, and perhaps even crusties desire a bit of bourgeois pomp on these occasions. Thankfully the irony is not lost on The Levellers' singer, guitarist and errant mouthpiece Mark Chadwick, who, bathed in the venue's sophisticated scarlet lighting, acknowledges how conspicuous he looks and feels.

As a slightly awkward introduction, Chadwick, with only violinist Jonathan Sevink on stage for company, announces how the evening will run. The first half of The Levellers' set is to be acoustic-based, showcasing the band's more mellow work, then, after a brief interval, the performance will turn electric.

It sounds an atypically choreographed affair from the now middle-aged nonconformists, but as the melancholic chords of "No Change" ring out around the venue, their well-oiled fans don't seem to mind. The song's sparse acoustic guitar and strings arrangement is reminiscent of Desire-era Bob Dylan, clearly an influence on a band who gamely romanticise "protest singers telling us what's wrong".

Multi-instrumentalist Simon Friend joins the band onstage for "Elation". Dressed in Cromwellian chic, his shoulder-length curls framing his face, he unleashes a voice that is easily as angsty and emotive as Chadwick's.

With the first half of the set gathering steam, the stage steadily fills – initially with the remaining members of The Levellers and then with a string quartet, bongo players and backing vocalists. The sound grows likewise, blooming from the frugal stirrings that opened proceedings into a pounding, electric-folk backbeat. However, the louder things get, the more the songs merge into one another, with melodies repeating and the stripped-down songs lacking the electric fizz they have on record. It's a limp climax to the first half of the set.

Now, I'm not sure how potent the organic pear cider is at the Royal Albert Hall, but as they stumbled back to their seats after the interval, The Levellers' fans were, in Chadwick's words, "definitely up for 'avin it". As the band tear into 1997's hit single, "What a Beautiful Day", the auditorium erupts into a dancing, wailing, dreadlocked monster.

Succumbing to the singer's trite demands to "rise up as one and start a revolution through dance", the crowd use the song as a rallying call, though its chest-beating sentiment seems little more than a nostalgic relic today.

Soon the inevitable Stop The War banners are waving in the front row, whistles are blown in and out of time with the music, and sweeping, grandiose strings drench the stage. As the set rumbles on, streams of high-tempo folk-punk are unleashed, the pounding beat utterly relentless.

The lyrics may be increasingly clumsy as the band clamour for contemporary relevance but the way they're playing is so full of Poguesian spirit it nevertheless sounds rousing. "Carry Me" breaks the mould slightly, introducing mild balladeering to the mix, giving the band's aging fans a well deserved rest before the final onslaught of "Men-an-Tol" and "One Way".

Things take a dip during the encore as the band veer off into songs from their experimental wilderness years – the awful rap and acid-drone of "This Garden" a particular low-point. However, as the band stutter to a close and the circus rolls out of town, the bewildered looks on the ushers' faces say it all.

Over their 20-year existence, The Levellers have frequently been misunderstood and perhaps unfairly written off as a niche band for social rejects. Sure, they wear their clichéd hearts firmly on their sleeves but it's something of a relief to see a band that still believe in something. Whether they have another 20 years in them remains to be seen, but judging from the reception they got here, their freaky fans may just demand it.