If I ever have an excuse to walk down Roupell Street near Waterloo station, I generally take it. It's a 1820s Georgian street, which has managed to survive developments, bombings and the expansion of the railways - walking down it is like walking back in time, or walking down a film set (which it usually is - you'll probably recognise it from Legend, The Boat That Rocked, Call the Midwife and oddly enough, the opening credits for Ant and Dec's Saturday Night Takeaway). I think places like this sum London up; pockets of history hidden away between big glass modern buildings, workers cottages built on marsh land which are now worth over £1m. Of course, in London there are places which are just as old, if not older which have survived - massive parts of Notting Hill and Holland Park for example, but they were built for the rich, whereas Roupell Street was built for people who needed a place to live - I often wonder what the people who lived there when they were new would think of what it's like now, and if they'd laugh? Either way, a roast at The Kings Arms is usually worth a shout (despite slightly odd gravy choices) and Konditor & Cook isn't a bad choice for a cake either.
Let me know if you know any other little gems like this hidden away in London!