A friend of mine was visiting from Alaska for the weekend and so I was looking for a place with atmosphere but away from the crowds. For those purposes,
this place was great. Situated in the Hays Galleria on the south bank of the River Thames, there is plenty of atmosphere and a view of the recently developed London skyline.
There were three of us eating and drinking here at lunch time. We ordered two club sandwiches (chicken, bacon and avocado) and one steak sandwich, all were served with fries. The chicken was plentiful but slightly dry and the volume of white bread did not help matters. Not impressive. I understand that the club sandwich was much better.

Club Sandwich, Balls Brothers
However, if you are looking to sit outside but are unsure whether the weather is going to stay on your side, this area is ideal. It has a clear plastic roofing (which is much more tasteful than it sounds) which shelters you from wind and rain. Not a bad place to stop for a drink.