In a recent, excellent, Vittles post, Jonathan Nunn asked people for the top five places visitors to London should eat at. Here are mine, based around the criteria of getting things you can’t get elsewhere/understanding the “soul” of London:
St John, but just for starters and puddings (whoever says the food at Rochelle Canteen is better is wrong, I always leave the latter feeling ripped off). You could substitute this with F.K.A.B.A.M., which offers an insight into both Turkish and nose-to-tail cooking, but the food is less consistent and the atmosphere is less fun.
40 Maltby Street, for the other side of Modern-British-Cooking.
Dishoom: not for the food, which is awful, but because it gives you a better insight into how white people view British Asians than almost anything else.
Bake Street, which gives you a better insight into how brown people view being British Asian than almost anything else.
Taste of Pakistan on your way back to Heathrow. Pack leftovers for the plane and annoy everyone on your return flight.