London is one of the greatest cities in the world — but one of the best things about it is how easy it is to leave. Within an hour, you can be walking along a seaside pier in Brighton, touring Windsor Castle, or wandering the colleges of Oxford. Travel a little farther and you can explore Roman Baths, medieval cathedrals, dramatic white cliffs, or even hop on the Eurostar and have lunch in Paris. The UK’s train system makes day trips from London incredibly simple. Most of the destinations on this list are direct routes from major London stations...