A man arrested on suspicion of murdering a suspected burglar has been released without charge.
Richard Osborn-Brooks discovered two intruders at his home in South Park Crescent Hither Green, south-east London, on Wednesday.
The 78-year-old was arrested after Henry Vincent, 37, from Kent, was fatally stabbed during a struggle in the kitchen.
The Met said Mr Osborn-Brooks had been released and would face no action.
Det Ch Insp Simon Harding said: "This is a tragic case for all of those involved.
"As expected with any incident where someone has lost their life, my officers carried out a thorough investigation into the circumstances of the death."
Police said they were called at about 00:45 BST to the property over reports of a burglary when they found Mr Vincent collapsed in nearby Further Green Road.
A witness said an accomplice dragged Mr Vincent toward a van before leaving him for dead. A second suspect fled the scene and is still being hunted by police.
Analysis, Simon Jones, BBC News
When we look at the law it is all down to what is considered to be "reasonable force" when someone is defending their home.
The law was clarified in 2013 to say if it was a highly stressful situation and if someone was under a great deal of pressure, then it would not be against the law to act using reasonable force.
It's always debateable what reasonable force actually is. But there was an assumption that if someone entered your house and if you were genuinely petrified and you did take some action, such as we had in this case, then that could be considered reasonable.
Mr Osborn-Brooks was held on suspicion of murder and released following a consultation between Scotland Yard and the Crown Prosecution Service.
His arrest had provoked outcry from neighbours and an online fundraising campaign.
Det Ch Insp Harding said: "While there might be various forms of debate about which processes should be used in cases such as this, it was important that the resident was interviewed by officers under the appropriate legislation; not only for the integrity of our investigation but also so that his personal and legal rights were protected."
In January, Mr Vincent was named and pictured by Kent Police investigating a distraction burglary on a man in his 70s.
Family and friends paid tribute to him on social media.