The law was updated in 2013(?) to clarify the position after the Norfolk farmer case. That case was complicated because the farmer insisted on playing with words that would challenge the law, refusing to make the simple statement required. The fact that he shot the invader in the back was irrelevant as it was totally dark at the time.
In the latest case, the bad guy didn't deserve to be tackled by a 78 year old hero more than twice his age and killed in the struggle - he was just an innocent family gang member who had already been to prison for serious offences, obviously needing more intense social reports and interventions and "lessons to be learned" about attempts to correct his recidivist behaviours.