One of London's main railway stations, Paddington is the main terminus for travel to the west of England. Much of the mainline station dates from 1854 and was designed by Isambard Kingdom Brunel. It of course is also where a certain bear called Paddington was found, and appeared in Richard Curtis' film About Time, so pay it a visit if you're a fan.
Know Before You Go: Guidance for travel in Great Britain and Northern Ireland