GBK was recommended to us by a good friend of my husbands on the premise that you wouldn't taste a better burger and also that we'd get a good deal if we surfed the net to find a voucher for a meal deal as the prices can be a little bit expensive. We opted to try the GBK in the Mailbox in Birmingham which is set in quite nice surrounds to the side of the canal although the views from GBK is mainly that of the opposite Tapas restaurant! Inside the restaurant is clean and tidy but nothing outstanding to look at but more what you would probably expect at a more up market burger restaurant. Whilst it was quite busy inside there was no wait for a table although I did notice later on people were waiting to be seated. The menu itself offered an impressive variety of burgers and on first sight (as they were delivered to other tables) they looked as impressive as they sounded. We ordered a buffalo burger and a minted lamb burger with a side portion of fries and onion rings. The food was top notch and I can't fault it, as was the strawberry milkshake which fills up 3 glass tumblers! We've since been to several different GBK restaurants and each one as impressive as the last. I would say though that getting a voucher off the internet is probably a must as you can actually save quite a lot and as you look around the restaurant a large portion of people have done the same!