There’s a movement gaining ground in London at the moment. As Byron Hamburger spreads across the capital with breakneck speed (and eventually capsizing aging Hamburger Unions and weary GBKs in its wake), the joy of finding a decent hamburger in the capital is becoming less of a rarity. I’m a big fan of Byron. They’re mainstreaming and quality-controlling the expansion of a decent burger experience. This is something London is not used to. At the opposite end of the scale, away from the building sites and the neatly printed menus and expensive agency branding, you’ll find The Meatwagon. Behind a large van in a very typical Zone 2 industrial estate a few minutes walk from Peckham Rye station, sits an unbranded, unassuming little food…