A Polish decorator battered his ex-girlfriend to death during a frenzied attack at her Hendon home after discovering she had started a new relationship, a court heard this week.

Mariusz Kolodziejczk attacked 29-year-old manicurist Katarzyna Koziol during a row on December 21 last year, and left her lying unconscious in bed overnight before calling an ambulance the next morning.

Ms Koziol suffered more than 50 injuries in the beating, including 12 to her head and neck, and she died in the Royal Free Hospital, Hampstead, from a severe brain haemorrhage in the early hours of December 23.

A jury at the Old Bailey heard on Tuesday how her nine-year-old son was in the flat, above a row of shops in Brent Street, at the time of the attack.

Kolodziejczk, 35, who denies murder, had abused and assaulted his partner during their three-year relationship, with Ms Koziol telling a friend she had been hit in the face in 2004. The following year Kolodziejczk ended the relationship and moved back to Poland for a short while.

During this time Ms Koziol began a new relationship with another man, and a month after returning to Britain, Kolodziejczk found out about the affair.

Prosecutor Peter Kyte QC said: "This made him furious. He made a number of insulting and aggressive phone calls even though by that time he was living with another woman."

On November 15 he visited the flat and tried to choke Ms Koziol, before throwing her against a wardrobe. She refused to press charges, but had a panic alarm installed courtesy of the victim support service.

Kolodziejczk sent flowers and text messages begging for forgiveness and declaring his love, before assaulting her again on December 21.The following morning he called a friend to the property and showed him Ms Koziol lying in bed under a blanket. She had a black eye and her face was swollen. It is alleged Kolodziejczk said: "I hit her. She fell off the bed so I picked her up and put her on the bed."

An ambulance was called at 8.20am, but Mr Kyte said: "Her condition was too serious for a brain operation and it was plain she was not going to be able to survive."

The trial continues.