A fact I just found out when I thought I better check the location.
Ironically now I know they're all over the place it seems like the one we went too, between Picadilly & Leicester Sq, isn't.
TGI must have got the better of it.
We went to http://www.edseasydiner.com/our-food/ Leicester Square.
I don't imagine for one minute it holds a candle to any of the burgers mentioned on this thread.
But it's a little diner, down a side street, round the corner from a massive TGI Friday's, which in my book gives it some brownie...