Gone are the single doors we're used to seeing in today's carriages, replaced by double doors spread across the train. They're wider too, allowing people to get on or off a lot quicker, easing congestion inside a particularly busy station. TfL will also ditch paper advertising boards for "dynamic" digital screens that can be automatically updated with Tube statuses and real-time travel updates, but also allow advertisers like Amazon to hawk its latest Kindle using video ads. There'll even be interior LED lights that will use a glowing traffic light system to warn passengers when they're about to open or close.

TfL plans to deploy 250 of these next-generation Tube trains on the Piccadilly, Bakerloo, Central and Waterloo & City Lines over the next decade, increasing the capacity on all four lines by a minimum of 25 percent (or 12,000 travellers an hour). They are intended to last for 30 years and run 24 hours a day, maybe for when Transport for London decides to allow all Tube trains to run around the clock without a driver. It expects the first PriestmanGoode-designed carriages to go into service on the Piccadilly line in 2022, completing its full rollout by the mid-2020s.