We also sampled a made-in-London local brew while visiting our friends in Hampsted, a 45 minute ride from central London. The Flask, as the pub was called, had Sambrooks "Wandle" on tap and it was worth the work on the beer engine especially since I wasn't the one working it. The cask ales don't have a lot of carbonation so the ale has to be pumped up by hand using that engine.
Close to our hotel we visited The Drayton Arms and tried some "Bishops Tipple" and some "Oxford Gold." Once again, we had no complaints. The CAMRA and Cash Marque websites offer lots of information so anyone planning a trip can find some tips before they leave. Cheers!