A sumptuous pink light radiates from one corner of London’s palatial Somerset House. The doors are locked and the building is empty, but it’s like something is still going on. Some glorious colour photographs peek through the elegant windows. They belong to Chris Stein, the co-founder of post-punk pop band Blondie. The exhibition has proved so popular that it’s been extended until 8 February. Have a good look if you can, rather than just a tantalising glimpse.