I really like London Walks. Among others, I've taken a Hampstead walk (don't remember which one though), the Jack the Ripper walk, the Legal & Illegal London walk, the Darkest Victorian London walk, and the Little Venice walk.
I really enjoyed getting to meet Donald Rumbelow during the Ripper walk. Richard III led the Victorian walk and was amusing and very informative. Shaughan, though, he has the voice and bearing of an actor - which he is - and had a fairly large group laughing during Legal London. I got him again on the Little Venice walk, and he was equally entertaining. I would go on any walk based solely on the fact that he would be guiding.
Little Venice itself was very interesting. It's an area I didn't know much about, so I had no idea what to expect. It made for a thoroughly enjoyable few hours. I definitely recommend it.