The glass to this ellipse is slightly silvered like a ghostly curving mirror, which means it plays gentle optical tricks on you when you are in it. What's inside, what's outside? The boundaries are blurred. The flooring - squidgy black rubber playground material - is the same inside and out. Dan Graham wanted to call this elliptical room "Waterloo Sunset", after the Kinks song (discussion of pop music, whether Kinks or punk, was a key feature of design meetings, according to Haworth). After some negotiation with Ray Davies of the Kinks, the name was approved.

This is a true collaboration between a very architectural artist and a very arts-minded architect. You don't have to go looking for the join between their different spheres of activity. However, you could certainly say that the "Waterloo Sunset" mirrored ellipse is very much at home in the Dan Graham canon while the expanded foyer box is a more straightforwardly architectural response to the pragmatic needs of the gallery: more and better lobby space, necessary things like better disabled access, and a friendlier, more open face to the world.

So there's nothing too monumental going on here. This is deft, relatively unassuming stuff, and it takes skill and a degree of affection to do that. This old bruiser of an arts building is looking pretty good on it. The old dog has life in him yet. And if it can be done here, then maybe the sleeping curse that lies heavy on the whole South Bank complex can finally be lifted.

The Hayward Gallery reopened with the exhibition "Saved: 100 years of the National Art Collections Fund" on October 23. Website: www.hayward.org.uk