Nas photos by Victor Frankowski

"Lovebox, I want to see you go absolutely bananas!" A small crowd obliges to the throb of Bashmore-house, having gathered around a pop-up wrestling ring in the middle of Victoria Park. This is just one of several baffling stages on site, joined by a garish Lewis Carroll manor house and DISTRIKT's dystopian dance shelter straight out of Terminator 2. There is also a roller disco, dodgems, several brand-sponsored busses, fairground rides, and a field of 15ft flowers towering above the piles of discarded food containers. Even the fag stand seems to have been constructed by Willy Wonka's own fair hands; cigarettes have never looked so fun.

Lovebox is less a music festival than it is a giant playground for dolled-up twenty-somethings to spend cash and take selfies in – hopefully a nice time will be had along the way. Despite a forecast of torrential rain, the sun on Saturday is unforgiving. Shady spots are few and far between and the bar queues stretch out of their designated tents and into the next. After standing sweaty and unsatisfied for 45 minutes, shirtless guys emerge with crates of Cidre and Becks draped across their shoulders like wounded soldiers, carrying them home to the troops who wait eagerly beside the bogs – heroes of the hour. Others forgo the bars completely to buy pills off bumbagged men, or the other Lovebox staple – laughing gas at "three for a fiver". A few vendors are even accepting card payments.

Admittedly this festival isn't meant for me, but it's a questionable setting to celebrate the 20th anniversary of Nas' Illmatic. It's as brash and loud as its headliner M.I.A, whose lyrics adorn the colourful signs above the entrance. By contrast, if Illmatic were a movie it would have been shot in monochrome. The lingering camerawork soaks up each and every detail, from the boombox that will chew your tapes through to the speck of ash that falls from a lit blunt. Yes, Illmatic is a classic in terms of its content, execution and impact – quite possibly the classic – but it's also a classic in style. It's many other things too – densely written stanzas, incisive social commentary and utopian dreams. It's the story of America's largest housing project; Queensbridge – dirty, dangerous and neglected.

One thing Illmatic isn't is the feel good hit of the summer. Beats from DJ Premier, Pete Rock, Large Professor and Q-Tip may fool you into thinking otherwise, but there are few happy moments to speak of let alone happy songs. Yet here we are at Lovebox, where furries and Illmatic fanatics stand side by side. One man has actually come dressed as former Bayern Munich goalkeeper Oliver Kahn ­– another legend who made his national debut in '94. It's probably a coincidence, but before I can investigate we're interrupted by the familiar rattle of a New York subway car. 'The Genesis'. It's a sound that evokes so many things, not just through its connection to Illmatic, but to Wild Style, Grandmaster Caz and the birth of the whole damn thing. "Stop fucking around and be a man" runs the sample, as the big screen counts back the years. At least for a few moments this could be any stage in the world. DJ Green Lantern queues up the next track, and Nas enters from stage left.

Donning limited edition Air Max, not much has changed – Nas is still a Nike-head, wearing chains that excite the feds. A pair of baggy black shorts and a commemorative Illmatic T-shirt completes the look, which is relaxed to match his demeanour. That's been the way lately, from his upper echelon 2012 album Life Is Good to a sage guest verse on the remix of J. Cole's grovelling lament, 'Let Nas Down'. The baby-faced rapper is growing older with grace, accepting his cushioned position in the rap cannon and having some fun with it.

As if phased by the occasion, the system stutters midway through 'The Genesis' – it's probably only 30 seconds of muted volume but it feels like minutes. Those minutes are precious to Illmatic, which is over and done in less than 40. Now I can hear it though, the pulsing bassline of 'NY State Of Mind' and Nas slipping into a trance. These are the bars that he wrote as a teenager but have come to define his life – followed into stardom by the clicking and clacking of ammunition that is buried within his own internal rhymes. The flow is still flawless, words unfurling from his lips with the satisfaction of falling dominoes. Trying to keep up is a pointless exercise, but it doesn't stop those in the first few rows performing for the cameras. Hundreds of listens in these verses are still turning over new tricks, so you're better off letting them wash over you and waiting for your signal.

This means the hooks and soundbites, which bounce around the festival crowd as readily as they have the hip hop lexicon. At least most of the crowd – a few are distracted by a fella with an umbrella who's been trying to stand on his mate's shoulders for the majority of 'The World Is Yours'; its message applied far too literally. A slim, landscape screen at the back of the stage helps retain the focus, displaying black and white footage of Queensbridge stairwells, vintage music videos and the red-hot steel of New York industry. It's a simple but significant addition, helping the audience to remain locked in to time and place. Perhaps it's drifted over from the nearby porter-loos, but I can almost smell the stench of pissy elevators on 'Represent' and the waft of weed smoke from the park on 'Memory Lane'.

The album plays through in sequence, with Nas offering only a few annotations along the way so as not to break momentum. 'One Love' is imbued with all of the gut-wrenching power you'd hope, as the narrator takes some time to explain how his prison letters are still painfully relevant twenty years later – "Out in New York the same shit is still going on." Looking out amongst the crowd he spots kids younger than the album itself, pausing to point out a sample or two. Michael Jackson's 'Human Nature' is even afforded a tribute of its own, MJ's face appearing briefly on the screen before it jumps abruptly into 'It Ain't Hard to Tell'.

And then it's over, just as quickly as it feels on record – quicker even, cut shorter still by the absent AZ for the record's sole guest verse. It's not the end of the show, there's a second act to follow made up of greatest hits. 'The Message', 'If I Ruled the World', 'Made You Look' and 'I Can' are among them; some of these songs are received even better than the Illmatic cuts, a testament to a career which is often discussed in too simple terms. Today was about Illmatic though, make no mistake. An album of its magnitude deserves its own platform, and none of the luminous attractions at Lovebox come close to matching its shine.