Just next to Farringdon tube station, The Castle is always a lively little pub that gets particularly crowded on weekends. Plus points are the retro space invaders table, good food, Belgian beer, British ale and a pool table upstairs.
Downsides are tiny tables and stools to sit on and ravers revving up for Fabric on Friday and Saturday. But you might be one of these people and enjoy a good electro warm-up and an 80's video game duel.