We're planning to have Nigel Wrench, or a shadow of him, live from Trafalgar Square on PM this evening. He writes:
"Take a look at this....
"...part of Under Scan by the Mexican-American artist Rafael Lozano-Hemmer, being installed as I write in Trafalgar Square, and available to experience each evening for the next ten days.
"The idea is that when you walk through a spotlight, a video of someone else is projected into your shadow.
"Mr Lozano-Hemmer installed a version of this work in Leicester, Northampton, Derby and Nottingham in 2006, when these pictures were taken.
(All images by Antimodular Inc [Copyright Rafael Lozano-Hemmer], courtesy ArtReach and East Midlands Development Agency)
"The promoters say the Trafalgar Square version will be 'the world's largest interactive video installation', and that the area will be flooded with '110,000 lumens of light', though I'm not sure how bright a 'lumen' might or might not be.
"They say there are up to 1,500 video portraits available, some taken during the East Midlands run, others filmed at Tate Modern in London this autumn.
"The art world regards Mr Lozano-Hemmer as currently 'hot'.
"So hot that Dasha Zhukova, curator of Moscow's new Centre for Contemporary Culture, commissioned him to make a seven-metre spiral of lights as the centrepiece of her gallery's opening last June.
"At the opening party, those outside the art world may have recognised among the guests Ms Zhukova's consort, the oligarch and football enthusiast Roman Abramovich.
"If you can't make it to Moscow but happen to be in London soon, there are two other (free) opportunties to see Mr Lozano-Hemmer's work: at the Barbican Centre and at a commercial gallery called the Haunch of Venison, which is owned by the auctioneers Christie's.
"The artist should be in Trafalgar Square live on PM with me this evening, when he and I will be trying the piece out, and attempting to make it work on the radio.
"Or did you experience it in the East Midlands two years ago?"