Valerie’s Snack Bar (2009).

I wasn’t sure about the Jeremy Deller show at the Hayward before I got there: Joy in People, he’s called it, ugh, and my friend had been complaining about the installation that re-creates his bedroom at his parents’ house, and the one that’s done as a market-traders’ café and gives you a free cup of tea. ‘They just can’t bloody resist it, can they,’ she said sadly. Like me, she’s a Deller fan of many years’ standing; I remember us both admiring the Folk Archive when it first appeared at Tate Britain in 2000. She was disappointed, I think, in the autobiographical aspect of these installations, which were a bit too close to Tracey Emin’s bed and hut.

She went on to talk about her first sighting of Baghdad, 5 March 2007, the oxidised wreckage of a car blown up in the Al-Mutanabbi Street book market, killing more than thirty people. Deller had tucked it under the Spitfire in the main hall of the Imperial War Museum: a completely brilliant thing to do, and for a piece of art put somewhere by an artist, unusually ego-free. And yes, the wreck is there in the Hayward retrospective, but as part of a bigger work called It Is What It Is (2009), which involved towing the car round the US with an American soldier and Iraqi civilian available at all times for free discussion. Which was also a brilliant intervention, and probably relatively ego-free at the time, but inevitably becomes somewhat less so in recollection, in an art-worldy set-up.

So I was wandering round the Hayward, fretting about sentimentality and self-regard, charmed in spite of myself by the acid house to brass bands mind-map, the 'Unrepentant Smokers' procession banner. Then I found the section called My Failures, and my worries sank away. It wasn’t just the aborted plan for the Iggy Pop Life-Drawing Class, impressive though those reverently charcoal-shaded sinews can hardly fail to be. Neither was it the Tube map in the shape of a bicycle, rejected for being ‘confusing, which I suppose it was’. It was Deller’s proposal, put to the Fourth Plinth Commission in 2004, for a life-size, fully dressed mannequin of David Kelly, sitting sadly, looking down (‘Because some people may have forgotten who he was,’ as Deller has said). The piece is startling, hilarious, compassionate, as Deller’s very best work often is; unusually for him, though, it also carries an art-world resonance. There’s a memory in it of Mark Wallinger’s Ecce Homo (1999), the only really non-fatuous piece that’s made it to the plinth so far. And accidentally or otherwise, it makes the most fabulously sideways comment on the current exhibit, Elmgreen and Dragset’s kitsch boy on a rocking horse: ‘Is it a homage to Rolf Harris?’ as Boris Johnson apparently said.

I’d had to take my son with me round the Hayward, because staff at his school were having an Inset day. (Topic: ‘How To Engage Boys in Learning’. You start, apparently, by giving them the day off.) By and large, he was happier at the David Shrigley, running concurrently upstairs. Deller demands a bit more hinterland than most eight-year-olds have yet picked up – why does he care so much about the inner lives of Manic Street Preachers fans? Why did he bother copying graffiti from the men’s toilets at the British Library and what does it mean ‘to fellate the rear of Germaine Greer’?

But then, we came to the room about The Battle of Orgreave (2001), for which Deller organised a blow-by-blow re-enactment of the decisive struggle in 1984 between riot police and striking miners outside the Orgreave coking plant in South Yorkshire. My friend actually went to this, and said it was astonishing – former miners, battle-re-enactment enthusiasts and art-world luvvies up from London, all in it together for just one day. I’d meant to go, only then I didn’t, because I had a piece to finish for the LRB. My son liked the film of the event so much that he watched it twice right through. Why, he asked, do the battle formations used by riot police in the 1980s so closely resemble the Roman ones in his Asterix books? Is it because the re-enacters mostly do Romans-in-Britain battles? Or is it because there’s only so much you can do with a bunch of men with shields?

The other day, he came back from school and told me that all his friends have been playing Miners and Riot Police in the playground. I don’t know what the ‘Engaging Boys in Learning’ people make of this development, but Deller I hope would be thrilled.