If you like street food (who doesn't?) London will not disappoint you. There is an opportunity to ruin your diet in every neighbourhood of London so don't fight it and enjoy the delicious options these street food markets have to offer. Here are some of my favourites.
Set up every Wednesday, Thursday, Friday and Saturday on Rupert Street in Soho. This small but effective street food market is open from 11am to 3:30pm. Try the hamburgers and the pulled pork burger. Closest underground station is Piccadilly Circus.
Borough Market is a must when visiting London. Open everyday from 10 am to 6 pm this food market offers everything. Whether you want to shop groceries or have a quick lunch, Borough Market is the right place to be. Check their website for special events. I especially enjoyed the Duck Confit sandwich (6 Pounds). There is also an ultra cute restaurant called Padella which offers fresh pasta. Or you can eat yourself through the market by tasting a bit of everything :) Closest underground station is London Bridge.
Dinerama is open every Thursday, Friday and Saturday from 5pm. So it's more like an evening street food market. The crowd stops by to have drinks and a tasty dinner. The place is especially popular during warm summer nights. Closest Overground station is Shoreditch High Street. If you're around Shoreditch during the day try Shoreditch Boxpark or Pump Street Food Market.
I stumbled across this cute place on my walk to Borough Market. There are not many options but it's the perfect place to have a beer with friends and eat something. Also just loved the pink benches :) Closest underground station Southwark or London Bridge.