A roofer is facing life behind bars for stabbing his girlfriend to death as he ranted about "releasing demons" and "drinking blood".
Ivan Griffin, 24, had claimed he was mentally-ill when he killed Sabrina Mullings, 38, at her home in Upper Norwood, south London.
However, prosecutor Timothy Cray told jurors it was just an attempt to disguise the truth, which was a "very old story which has its roots in male anger and aggression".
Following a trial at the Old Bailey, jurors agreed and found Griffin guilty of murder after deliberating over two days.
Ms Mullings' mother Marian broke down in tears in court, supported by other family members.
Griffin appeared via video link from Belmarsh prison to hear the verdict.
Before the killing, Griffin and Ms Mullings appeared to be "loved-up" and talking about getting engaged and planning a honeymoon.
Just 12 hours before, the couple had been photographed by Ms Mullings' daughter dancing together, jurors heard.
On the morning of March 13, Ms Mullings' daughter Hayleigh was awoken to the sound of shouting coming from her mother's room at the one-bedroom flat they shared.
She and her boyfriend Chaise Gore went across the corridor and witnessed a scene of "fear and extreme violence", jurors heard.
Mr Cray said: "At the start, Sabrina was still alive because they heard her speak.
"Some of the words they could hear from her were to the effect that the defendant was hurting her and she was asking for help.
"It was the defendant who was doing the shouting and his words were strange, talk like they had never heard from him before, along the lines of 'releasing demons' and 'drinking blood'.
"He would not let Hayleigh and Chaise into the room to see what was happening and their first view of what happened was through a pane of reinforced glass in the door that was broken in the struggle to get in.
"They also saw blood start to seep out from under the door."
By the time Griffin opened the door, the front room and kitchen was covered in blood and Ms Mullings' naked body was lying on the floor.
Although she had a weak pulse, she was "minutes or seconds from death" having suffered two stab wounds to her stomach and chest, the court heard.
Griffin told Hayleigh and her boyfriend that he stabbed her mother because he loved her and stabbed himself in order to "join their blood together".
The defendant, who had superficial wounds, was picked up by police later that day walking around south south-east London wearing nothing but a jacket.
Griffin had a previous conviction for assaulting a former girlfriend who had described him as having a "controlling and aggressive personality".
Mr Cray rejected the suggestion Griffin had developed a sudden and previously undiagnosed mental illness.
In a victim impact statement, Marian Mullings described her daughter as a "loving person who would very much wear her heart on her sleeve".
She added that Sabrina was an independent woman who had an artistic streak and gave birth to her daughter at the age of 16.
Sentencing was adjourned until a date to be fixed.
Detective Chief Inspector Will Reynolds of Scotland Yard said: "Griffin callously and viciously attacked a vulnerable, trusting woman that he purported to love and had asked to marry him.
"He subjected her daughter, Hayleigh, and her boyfriend to the terrible ordeal of hearing the attack on Sabrina but being prevented from helping her, and then callously fled the scene."