Update: Ring ahead before visiting to check they actually have a chef. Often I've rocked up only to find out the kitchen is closed because of no new hires.
Coach and Horses
The Coach and Horses pub, located on Greek Street in London's Soho, maintains a 100% vegetarian menu with a few vegan options. I have heard great things about the vegan "fish" and chips, but all my attempts to try it have been thwarted by things like accidentally getting drunk and eating falafel instead. Finally, finally I made it to this Soho corner bar on a quiet weekday afternoon, and I'm glad I did. The faux fish itself isn't anything to write home about – it's little more than battered and fried tofu with some nori for a fishy taste – it's the tartar sauce that makes the plate. My only complaint is the peas ought to be marrowfats and mushy since what else would you eat with fish, but other than that it was one of the nicest comfort meals I've had out in awhile.