A talented academic was stabbed repeatedly, beaten, strangled and suffocated in her North Oxford home by a man torturing her for her bank details, a jury heard.

Michael Humphries, of Ferndale Street, Faringdon, is accused of murdering 55-year-old Barbara Johnston in January. He denies the charge.

Oxford Crown Court yesterday heard that Dr Johnston, a medical researcher who had worked around the world, was stabbed 49 times and found lying in her blood-stained flat with a jumper around her neck and another around her wrist. Prosecutor Richard Latham QC alleged that 43-year-old Humphries, who had carried out double glazing and DIY work for Dr Johnston a month before her murder, went to her home and repeatedly stabbed her to force her to give him her PIN.

Mr Latham told the jury that Humphries, who was unemployed at the time of the killing, was "clean out of money" and being pursued for cash over a hire car he was using.

He said that there were no witnesses and it was a "good old fashioned detective story".

Detectives believe Dr Johnston was still alive at 10am on Tuesday, January 24, because she logged on to her computer.

But less than an hour later, £200 was withdrawn from a cash machine at the BP garage at the Pear Tree roundabout, near her home in North Oxford.

The Peugeot 206 van Humphries had hired from Faringdon garage was spotted on CCTV there, but no images of him were found.

Mr Latham said: "We will never know precisely what happened, but we may conclude that someone got out of Barbara Johnston her PIN number and one way to get such a sensitive piece of information from someone if they are stubborn and do not want to give it away would be to stab them with a knife.

"By the time the cash was being withdrawn from Dr Johnston's bank account she was dead or in the process of dying.

"This defendant - whether he went there Dr Johnston's flat for money or not - got to a stage where he had to kill her because he had already hurt her to extract her PIN number.

"He left her flat and locked it. During the next few hours he got rid of the clothing which linked him forensically with what he had done."

The court heard how there was no sign of forced entry.

Dr Johnston bought the flat in 1996 but rented it out while working abroad. She had returned to the UK in August 2005, after working in New Zealand.

The court heard that Dr Johnston was a single woman with a number of friends who was close to her elderly parents, Anthony and Valerie, and kept in touch with them.

The trial continues.