The boyfriend and I hopped on a train from Birmingham to London last month, and decided to spend a whole day in the capital city. It was a strange day, as the public transport system failed up the entire day (delayed trains, closd tube stations, etc) but we still managed to have a nice day and I know that I'll be back there soon! There's always something to see in London, and I don't think I could ever run out of things to explore.
