He may not have filmed a single second of it, but Mr Christian Marclay’s “The Clock” is a masterpiece of video art: 1,440 minute-long, painstakingly researched clips from thousands of different film and TV shows, depicting a peripatetic 24-hour day, in real time – whether it’s a close-up shot of a character’s watch, a clock in the background, or an alarm clock “kerchunking” from 5.59 to 6.00 (Groundhog Day, natch).