Best Northern Vietnamese cuisine in London are The Viet Grill and Cay Tre. They do all the best stuff from Hanoi (also some special from Ho Chi Minh City). Their chef is from Hanoi and he has a best knowledge about Vietnamese Food. (I heard this from the first secretary of the Vietnamese Embassy in London, he said the embassy often books for party their)

Try the Pho Cuon Steamed Roll, The Cha la lot (spiced meat wrapped in betel leaves), and the turtle (24 hours notice) and you will be amazed.

The pix of the the quail looks really promising. About the feudal beef, it looks so much like a english steak. Does is taste the same?

Vietnamese cuisine uses a lot of different herbs, the most popular one is Thai sweet basil and rice paddy herb.

Cay Tre is more like for Noodle Soup, it has the best broth and stock for soup. Really good food but it is so busy.

Viet Grill is more relaxable and you can have fanstastic dish from grill, but it lacks of the ambience like Cay Tre though