A "callous" and "selfish" man has been jailed for life after drowning his nine-year-old grandson in the bath.
Stewart Greene, 65, killed Alex Robinson at his Lincoln home two days before Christmas while members of the family went food shopping.
Greene, of Danes Court, Grimoldby, Lincolnshire, had claimed Alex's death was as a result of diminished responsibility and denied murder.
But he changed his plea eight days into his trial at Lincoln Crown Court and was today told he will serve at least 22 years behind bars.
Sentencing Greene, Judge Mrs Justice Thirlwall said: "The callousness cannot be overstated.
"During the course of this trial, you have sought to manipulate everyone in the court room.
"You manipulate people to get what you want.
"This was not the product of mental illness, it was wholly your responsibility."
She added it was a "terrible act".
"Your concern was for yourself, 'will I go to hospital?', 'I can't do prison'.
"You describe yourself as having been selfish all your life, of that there is not the slightest doubt."
The court heard Alex's mother Joanne Greene had left her son in the care of Stewart Greene while she went shopping for a turkey on December 23 last year.
The youngster, who was on the autistic spectrum and didn't like having water on his face, was playing on his XBox when he was left with Greene at the house in Pennell Street.
Greene then locked the doors, ran a bath "with both taps to fill the bath even more quickly", walked his grandson into the bathroom and drowned him.
The court heard he then rolled a cigarette and waited for the family to come home.
During the trial, prosecutor Michael Evans QC said Ms Greene returned to find her father sitting calmly on the settee.
According to the prosecutor, Greene told his daughter: "I've drowned Alex in the bath."
The court had previously heard Greene had been discharged from a psychiactric unit and hated the idea of living independently at accommodation arranged for him.
Giving evidence, Ms Greene said her father had a history of depression-type illness and had been admitted to a mental health unit earlier in the year.
She explained how, a month before Alex's death, she had pleaded with staff at a unit not to let him out.
She said this was because he did not like living independently, outside of residential centres, and had attacked people before, including trying to strangle a doctor, in attempts to stay as an inpatient.