The ghost of Duveen still enshrouds this gloomy colonnade - an obstacle to be surmounted in any serious effort to use this ample space for the display of art today. Wallinger now brings all this pomposity down to basement level. His variant of urban graffiti, inspired by and borrowed from Brian Haw - banners placards, fabric swathes and instant barricades - all call down our scorn on the beleaguered Prime Minister. This is a simulation of the powerful protest wall erected by the intrepid Haw. The 1 km exclusion zone imposed actually falls completely short of Tate Britain and Wallinger's later installation. However, the artist still has the onus of proving where the exclusion line passes, although it is outside of his Tate Britain pitch, placing a line of black tape along the floor of the gallery. To give Wallinger his due, the real hero - whom he duly celebrates - is Haw himself.

One has to ask what Wallinger is actually able to achieve in this simulacrum. After all, with William Hogarth's work now arriving from a successful showing in Paris, the quality of Wallinger's intent will have to be on a very high level not to grate against Hogarth's famously telling wit and satire in the same building. Wallinger's presentations vie with a massive photograph of Blair, Brown and Straw all dipping their hands in Iraqi blood, in the shadow of Pontius Pilate's 'He took water and washed his hands before saying, I am innocent'. Hogarth would not turn a hair at the baby victims of Baghdad bombs, limbs and scattered fire. The dolls nearby, in Victorian infant garb, and damaged cuddly toys all conspire to illustrate the artist's own horror at man's inhumanity to man. Like Hogarth, Wallinger reveals a quality of Englishness not much changed in 250 years and not entirely palatable, mixing blood and games nonchalantly. But this, as Brian Haw also intended, covers factors of human identity and of national roots and belonging. We should freeze-dry what remains.

Wallinger draws William Blake into his small talk as another radical, scrawling out the word 'Jerusalem' as a symbol of the unattainable. Sadly, there is no Wallinger racehorse; that famous creative act when he acquired a racehorse and registered his own racing colours (quel panache!), entitled 'A Real Work of Art' (1994). Here, Wallinger seeks out a well-established concept of modern art that is site-specific, and creates a bricolage of famous writings, from Thomas Jefferson, for example, all in the name of 'freedom'. So, is Wallinger's work a full critique of the Tate as an institution? Perhaps not. Tate Britain and Modern, too, are characterised by a degree of soft liberalism in all its tendencies. 'State Britain' also steps back from such a total critique, mocking instead our wider cultural and social structures. Where better than in the shadow of crafty Duveen? And what of Wallinger's so-called 'line of exclusion'? His 1 km line of black tape runs into Tate Britain, then traverses past the well-recognised bust of TE Lawrence (perchance another protester), eventually goes past Jacob Epstein's 'Jacob and the Angel' and shoots past the petite portrait by Nicholas Hilliard of Elizabeth I (no stranger to blood on the hands). The line seems to run out of momentum as it hits the wall just below 'Reapers' by George Stubbs (1785).

In this way, Wallinger opens a discussion between himself and the museum. But sadly enough, this actual exclusion zone is a bit of a fantasy (or perhaps one should say 'artist's licence'): the line falls far short of Tate Britain's building. This fallacy is redolent, too, of the abandonment of credibility in Blair's Britain. What Wallinger is pushing for at Tate Britain is a heightened sense of reality (ie what the racehorse in Wallinger colours was all about, but in art). This simulacrum, of a very moving protest by Brian Haw, just seems to push truth and reality further afield and apart. The fantasy 'exclusion' does not help anyone.

Michael Spens