Grand Designs: Most Challenging Builds

Another chance to see the 100th episode of Grand Designs, which is marked by a truly momentous project. Leigh Osborne and Graham Voce want to convert and extend a landmark 150-year-old, 100-foot-high water tower in central London. Grade II listed, but utterly derelict, with six-foot-thick walls and crowned with a huge steel tank: it's an almighty task. As if this isn't challenging enough, Graham and Leigh also plan to build two additional contemporary structures at the base: a new lift shaft connected to the tower by a series of glass tunnels, and a modern living space nicknamed the 'Cube'. Altogether this cluster of buildings will create a four-bedroom luxury home over nine floors, crowned with a spectacular viewing room at the top offering 360-degree views across London. But a tight schedule and soaring budget make this a stress-laden build