The court heard that a third man thought to be involved in the attack was in all likelihood the prime mover in the crime, but is now dead.
The judge Mr Justice Saunders QC said Tom Curtis, the brother of Rocky Curtis, "was likely to have been the leader of this criminal enterprise."
Tom Curtis, 30, of Newbridge Lane, Wisbech, was arrested by police in connection with Sonny Gray's murder in December 2011.
He was recalled to prison in relation to other matters, but was later found dead. His death will now be the subject of an inquest.