Phoenix Spencer-Horn’s body was found on Glen Lee in East Kilbride, South Lanarkshire, in November last year.

Prosecutors said Ewan Methven, 27, attacked Ms Spencer-Horn by repeatedly striking her on the head and body with a knife or knives.

The court heard Methven choked Ms Spencer-Horn, before severing her head and trying to remove her limbs and torso from her body.

Tony Graham, Methven’s KC, entered guilty pleas to charges of murder and attempting to defeat the ends of justice at the High Court last month.

Methven is due to appear in the dock for sentencing on Monday morning.

Methven, now 27, murdered Ms Spencer-Horn, 21, in the home they shared on November 16 last year, after the couple ordered a takeaway to their flat in Glen Lee, East Kilbride on a Saturday night.

Earlier that day, Methven, who worked as a postman for Royal Mail, had complained to his girlfriend that her waitress shifts made him “lonely”, and she had exchanged messages with her mother, Alison Spencer, at around 9.37pm, saying they were eating dinner.

The couple had been together for two years and met at a family party, the High Court in Glasgow was told.

Around midnight on the Saturday, Methven attacked Miss Spencer-Horn with three knives, stabbing her 20 times, before mutilating her body and severing her head with three knives, the court heard.

He spent the weekend driving Ms Spencer-Horn’s red Corsa, scrolling through her phone and searching for internet pornography, as well as making several attempts to buy cocaine, according to prosecutors.

Prosecutor Christopher McKenna said: “The accused murdered his girlfriend, Phoenix Spencer-Horn, in the top-floor flat they shared. Late on Saturday November 16, he strangled her and stabbed her. He dialled 999 but not until November 18.

“Her mutilated and decapitated body was discovered only on November 18.”

The court heard that Miss Spencer-Horn had seen her mother the day before and had been in good spirits at work the day she was murdered.

Mr McKenna said: “The police recovered texts between the accused and Phoenix, he complained of feeling lonely because of the hours she worked and he apologised.”

The court heard that a food order was placed around 8pm and Methven “did not appear to be drunk or under the influence by the delivery driver”, however, in a 999 call, he claimed that the murder happened when he had a psychotic episode induced by cocaine, alcohol and steroids.