Edit to add - I also wonder if the Crown shouldn't have added GBH as a fall-back. You don't have to foresee the gravity of the harm to be found guilty of basic GBH, just be guilty of inflicting it.
From the articles it looks like he got into an altercation with the victim in the chicken shop, then him and his mates followed the victim out of the shop and into an alleyway. Then he beat him to death with a bike chain.
I want to read the case notes to see the arguments and how the judge directed the jury.
This version of the story makes it feel more open to jury interpretation
http://www.standard.co.uk/news/crime/decorator-cleared-of-beating-czech-man-zdenek-makar-to-death-with-a-bike-chain-in-poplar-a3506121.html
Still doesn't feel right, though.
Edit to add - I also wonder if the Crown shouldn't have added GBH as a fall-back. You don't have to foresee the gravity of the harm to be found guilty of basic GBH, just be guilty of inflicting it.