In the past Keith Wilson has turned puddles, mattresses, and images from particle accelerators into art. Now he takes the serpentine middle part of the Piccadilly line on the London Tube map and turns it into an installation that stands outside the Hayward Gallery. Large and steel and seeming to belong to a cattle ranch, it almost made me miss the entrance. That would have been a shame. The British Art Show 7, which ends its London run on April 17, is a lively snapshot of contemporary art in this country from the last five years, and something not to miss.

Go, get into the mind set of the artists — 39 of them and artist groups, top names and newer, British or based here — and allow yours to shift. Organised every five years within the Hayward’s touring programme — sadly not coming to Oxford — it was a sell-out in Nottingham last autumn.

Easily the most compelling piece is Christian Marclay’s The Clock (2010). This amazing montage of movie clips inexorably ticks through time, second by second, minute by minute, through a full 24 hours. Forget your own watch. The thousands of clips of clocks and watches, Big Ben, station clocks, fob watches, Rolexes, digital, and movie stars reacting to each and every one of them, move forward in real time. It is deliciously edited too, clever continuity knitting fragments of stories together. It’s obsessive, passionate and totally memorable. I could have spent the day there.

Every now and then a naked man enters the downstairs gallery to sit on a burning bench — Roger Hiorns’s Untitled (2005-10) — and Steven Claydon’s bell tolls in the stairwell. Upstairs, Juliette Blightman surprises with a net curtain and lamp in one of the Hayward’s austere windows, and Sarah Lucas shows strange bulging biomorphic sculptures.

There’s the expected mix of good, gritty, witty, weird, memorable and forgettable here, plus some that make you flinch. But few paintings — George Shaw’s of a Coventry council estate stand out — and little beauty, though Wolfgang Tillmans’s emerald green and black ‘free swimmer’ photograph made without a camera flows.

For information see: www.southbankcentre.co.uk