Why did London have to wait so long for a main-line railway beneath its streets? For a few years in the mid-nineteenth century, Isambard Kingdom Brunel's broad-gauge Great Western trains ran from Reading to Faringdon. Now, after many false starts, his vision is being realised as the Elizabeth Line prepares to carry passengers from Reading to the City once again, and beyond to Essex and Kent, using engineering that would have earned the admiration of the greatest Victorian engineers. London historian Stephen Halliday presents an engaging discussion of Crossrail's fascinating origins and the heroic engineering that made it all possible.