One of the first things you see in Mark Wallinger’s 40-meter-long installation State Britain, in Tate Britain’s Duveen Galleries, is a quote printed onto one of many apparently makeshift signposts incorporated into the piece. "When I pass protesters every day at Downing Street, and believe me, you name it, they protest against it, I may not like what they call me, but I thank God they can. That’s called freedom."

Four years after British prime minister Tony Blair said these words, on May 23, 2006, at 2:45 am, 78 police officers descended upon what had been the most dogged and visible protest against the invasion of Iraq, a giant, makeshift antiwar encampment outside the Houses of Parliament, incorporating contributions by hundreds of well-wishers and presided over by peace activist Brian Haw. The police, acting according to the newly passed "Serious Organized Crime and Police Act," removed and apparently destroyed the majority of the offending posters, placards and paintings. Today, Haw’s protest remains -- but the sting has been taken out. By direction of the police, his peace demonstration has been reduced to the size of a newsstand.

The new act designates a zone in which unauthorized protest is now an offence. This one-kilometer circle has its center point in Parliament Square, but, as it so happens, its perimeter neatly bisects Tate Britain’s Duveen Galleries a few hundred meters further along the banks of the Thames. Thus, for this show at Turbine Hall, Mark Wallinger has meticulously reconstructed every single tattered poster and battered placard in Haw’s protest, marking a kind of elegy to a semiotic shift, from one idea of freedom to another.

The installation runs parallel to the long sides of the Duveen Galleries and on both sides of the line, as if to dare the authorities. There’s no stepping back from it, no way of comprehending the whole, so you experience it as a sequence of images, like a scroll unfurling. If it is a memorial -- and its relocation and piece-by-piece reconstruction demand it to be read as such -- it’s along the lines of Maya Lin’s Vietnam Memorial, a contemplative horizontal rather than a triumphant vertical.

The smaller details of Haw’s protest -- a row of teddy bears carrying placards reading "Bears against Bombs," a tank of what might be piss labeled "Not Water," a ramshackle tea-making area -- benefit most from this relocation, bringing out the eccentricity and single-mindedness of the protest, which makes it seem akin to some kind of autistic folk-art environment.

On the other hand, the larger hand-painted signs are defanged by their new context. "Beep for Brian," once an irreverent call-to-arms taken up by many motorists plowing through the Westminster traffic, has become an absurdity, un-honkably sealed within the echoing marble box of the Tate. Never has the notion of the "lost original," that timeworn legacy of Duchamp’s ready-mades, carried such a melancholic charge.

Unlike Duchamp, who famously chose his ready-mades on the basis of their lack of any esthetic value whatsoever, Wallinger’s objects are suffused with an impotent homespun rage. Images of the process of reconstruction of the protest in the artist’s studio show Wallinger’s assistants working from projected digital photographs of the lost originals, taken by Wallinger a few days before Haw’s encampment was destroyed. An assistant carefully scuffs the text on the word "Killers." A steady hand replicates the drip of a spray can. It’s like watching artifacts being pieced together for a historical museum, which itself conveys a sense of a present brutally out of whack.

The curtailing of civil liberties that followed the sequence of disasters and deceptions after September 11th -- the Haw episode is one among many -- has naturally engendered a debate about national loyalties in the UK. What better place to discuss this than Britain’s state-sponsored gallery of art, where oddball provincialists like Stanley Spencer and the doomy romantic Pre-Raphaelites propose a Britain of weirdos and fantasists, of boggy Surrealism and nerdy Pop.

In this context, Wallinger and Haw’s do-it-yourself eccentricity and scatterbrained bathos has an unexpected rightness. Eccentrics dominate Tate Britain’s collection, and it is eccentricity -- as much as the freedom of speech and the freedom of protest -- that is at stake here. The black line that runs like a spine along the center of the floor and invades the adjoining galleries not only marks the limit of the one kilometer zone, it’s a bloodline that connects the work both to its heritage and to Wallinger’s perennial subject: what we talk about when we talk about Britain.

The pathos of State Britain only really takes hold once you realize that, looking at it, you’re doing something you wouldn’t otherwise be able to do. The antiwar protest itself has been all but swept under the rug by Tony Blair’s shenanigans, and those to whom it was directed no longer have to wince at blown-up images of Iraqi and Afghan children horrifically maimed as they leave the Houses of Parliament. No-one visiting State Britain is going to have their ideas about the Iraq war radically altered -- but neither can they fail to appreciate the seriousness of Wallinger’s gesture and the anxiety that underpins it.

State Britain could be compared with the great heritage of political protest in art, from The Disasters of War to Guernica to the contemporary installations of Jon Kessler and Thomas Hirschhorn. The latter’s Superficial Engagement, displayed at Gladstone Gallery in New York last year, with its similarly gnarly, scotch-taped esthetic, spoke to an audience who didn’t need persuading that the Iraq venture has had disastrous consequences.

Wallinger’s London installation is something different -- a monument to the idea of public protest against the war. The survival of Haw’s camp as art object and its death as protest are one and the same.

BEN STREET is a teacher, lecturer and critic living in London.