An 84-year-old man has admitted killing his nephew after mistaking him for a burglar.
Ezekiel McCarthy pleaded guilty by reason of diminished responsibility to the manslaughter of Desbert Welsh, 50, in north London in November 2011.
The Old Bailey heard that McCarthy, from Cricklewood, was suffering from an acute episode of delirium and early dementia when the attack happened.
He thought his nephew was an intruder and stabbed him, the court was told.
McCarthy denied murder and his plea to a charge of manslaughter was accepted by the prosecution.
The incident happened on 13 November last year at McCarthy's ground-floor flat in sheltered accommodation in Brondesbury Park, Cricklewood.
'He is destroyed'
The pair had been drinking and celebrating McCarthy's birthday of a few days earlier on 8 November, the court heard.
They arrived at McCarthy's home in the early hours.
In the morning, McCarthy knocked on a neighbour's door seeking help.
Jonathan Rees, prosecuting, said a woman friend saw McCarthy outside holding a knife with blood on it.
McCarthy told her: "This bloody man. I don't know how he got in my room."
He later told police: "I was defending myself."
Mr Welsh died three days later from a stab wound which pierced his liver.
Mr Rees said: "This is a dreadfully sad case involving the killing of a nephew by his uncle, thinking he was an unknown intruder."
Alex Milne, defending, said Mr Welsh's death had had an impact on the whole family.
He said McCarthy could not believe what he had done and could not associate the victim with his nephew.
"He is destroyed. He is mortified," Mr Milne said. "He could not in his wildest dreams harm his nephew."
McCarthy was released on bail until a pre-sentence report on 4 December.