This female-run, transatlantic business drops portrait artists into large and small events around London. Individual sketches can take as little as two minutes, but leave guests with an enduring memento. Talented enough to have been called in for events at Tate Britain, its artists roam free. Working on iPads, they carry mobile printers and, despite the name, there is no booth. Branding and hashtagging of the prints is easily arranged in advance.