A man has been arrested in connection with the savage murder of a female academic who was stabbed 49 times and apparently strangled with her own sweater shocked the university city of Oxford.

The body of Dr Barbara Johnston, 55, who returned to Britain just four months ago after working in New Zealand for 23 years, was found in her bedroom in the city's quiet northern suburbs.

Officers battered down the door of the medical researcher's one-bedroom flat just off Woodstock Road after her elderly parents raised the alarm.

Inside the property, which Dr Johnston owned, police found her body riddled with a total of 49 stab wounds, some deep, some shallow.

Around her neck was the sweater which police believe may have been used to strangle her.

But detectives have so far not identified a motive for the murder of the woman described by family as a "private" person.

Painstaking forensic examinations found no sign of forced entry, including on the outside where the building is cloaked in scaffolding, and nothing was taken.

Detectives believe Dr Johnston, who specialised in researching child respiratory complaints, may have opened the door to her killer or killers and may have known her attacker. She was fully clothed.

A 42-year-old man was arrested in the Faringdon area and is being questioned in connection with the murder investigation.