Police officers broke into a house to rescue a petrified woman whose angry lover was pinning her down by her throat, a court heard.
David Burnand (42) had already head-butted the woman three times and held a knife to her stomach, threatening to kill her.
When she tried to escape, he had dragged her back inside and threatened: "You're going to die in an hour."
Sentencing Burnand to two-and-a-half years in prison, Judge Simon Hammond said: "Heaven only knows what would have happened if the police hadn't responded and forced entry to save her. They may have saved her from a worse fate.
"This was a prolonged, brutal, pitiless assault on a woman who was vulnerable and much smaller than him," said the judge, who said officers in the case were to be congratulated.
Leicester Crown Court was told shocked neighbours alerted police after hearing the woman's screams, in a quiet residential street in Anstey, Leicester, on December 2 last year.
Philip Gibbs, prosecuting, said: "The victim was in a relationship with the defendant for 12 months. She'd changed her mind about selling her home and moving in with him and he didn't take it well and threatened to kill himself."
On the day of the incident, they each drank several cans of alcohol and an argument flared up.
Mr Gibbs said: "The defendant suddenly got a crazed look on his face, eyes bulging. He grabbed her hair and head-butted her three times to the top of her head with real force.
"He pulled her on to the kitchen floor, causing her to bang her head. He said he was going to kill her and walked over to the knife block and pulled out a knife as she got up. He got close to her with the knife and threatened to kill her. She believed him and began screaming towards an open window.
"She ran from the house screaming for help and banged on a neighbour's door. He chased and caught her. Witnesses described him as seething. Back indoors, he pushed her against a fridge, prised her mouth open and forced a tea towel into her mouth.
"As he was roughing her up, officers forced an entry. They saw the defendant with his arm around the victim's throat, holding her down. They told him to let her go.
"He was silent and just stared at the officers, who had to repeat their demands before he complied. He had her mobile phone in his pocket and there was blood on his fingertips."
Burnand, formerly of Anstey, but recently of Mona Road, Nottingham, admitted causing actual bodily harm.
He was made the subject of a restraining order banning any future contact with the victim.
Mr Gibbs said a victim impact statement described her as being in "emotional turmoil", unable to cope and on anti-depressants.
Sally Bamford, mitigating, said Burnand was of previous good character and references handed in to the court spoke well of him.
She said he was ashamed of what he had done.