A TAXI driver who killed a woman in a "frenzied" hammer and knife attack has been sentenced to at least 12 years in prison.

Martin Bell, 45, said God told him to kill 23-year-old Gemma Simpson at his flat in Harrogate in May 2000, and pleaded guilty to manslaughter on the grounds of diminished responsibility when he appeared at Leeds Crown Court this week.

The court heard Bell - who had known Miss Simpson for about five years - repeatedly struck his victim with a hammer, and stabbed her in the back and neck an "enormous" and "uncountable" number of times with a kitchen knife. He then filled a bath with water and left her in it for four days with her hands tied behind her back, and later sawed off the bottom of her legs when her body would not fit in the boot of a car he hired.

Judge Peter Collier QC gave Bell a life sentence and ordered him to serve a minimum of 12 years.

He said: "The killing of Gemma Simpson was brutal. Your treatment of her body after death was dreadful.

"But your culpability was considerably diminished by your mental illness."

Bell handed himself into police earlier this year and said he gave Miss Simpson the opportunity to get away but killed her after he thought she had threatened his children.

He has since been diagnosed with schizophrenia, and told police he wrapped Miss Simpson's body in a sleeping bag and secured it with chains and a padlock "so she couldn't get out", before he drove her to Brimham Rocks, near Harrogate, and buried her.

Paul Greaney QC, for Bell, said the defendant heard voices telling him to do things and had "developed complex delusional beliefs" which saw him moving around the country because he believed a group of men were trying to kill him.

He had been sectioned in a mental hospital for around nine months in August 1999 and was released around six weeks before he killed Miss Simpson.