In 1991, One Canada Square, the UK's tallest skyscraper, changed the London skyline. But the Cesar Pelli designed icon wasn't in the heart of the capital. Instead, the developers had taken a billion dollar gamble on creating an international financial centre, symbolised by this obelisk-shaped tower, in the desolate docklands of the city's East End. But when the world property market collapsed just after the complex was completed, the developers went bankrupt and a large part of the tower lay in darkness...