A woman serving a life sentence attempted to murder her friend on a train in a "severe incident of extreme violence", a judge said.

Lisa Savage, 42, had left her probation hostel in Birmingham and was heading to confront her mother in Aberdare, south Wales, armed with two knives.

Newport Crown Court heard Savage was accompanied by friend Sarah Hayton, with whom she caught a train from Birmingham New Street on April 15.

Lisa Savage after attacking Sarah Hayton. Picture: British Transport Police

They had to change trains at Gloucester, where Savage was seen attacking Ms Hayton as she was in a foetal position on the platform.

After they boarded the 10.33pm train from Gloucester to Cardiff, Ms Hayton told Savage she did not want to go through with the plan.

Savage stabbed Ms Hayton multiple times, mainly to the face and neck, in a four-minute attack that terrified fellow passengers.

During the incident, Savage told her victim: "Go to sleep, little girl."

The train was locked at Chepstow railway station after passengers and rail staff raised the alarm, but Savage managed to escape.

When she was arrested in a park hours later, she told police: "I took her out, didn't I? I f****** did it, didn't I? F****** brilliant psycho killer."

Jailed: Lisa Savage

Judge Eleri Rees, the Recorder of Cardiff, handed Savage a second life sentence and jailed her for a minimum of eight years and four months.

"You carried out a frenzied and sustained attack on her, stabbing her repeatedly to the face and neck," the judge told Savage.

"You also stamped on her legs. This was a most shocking incident for other passengers and train staff."

The judge described the attack as "a severe incident of extreme violence".

Savage pleaded guilty to attempted murder and two counts of having an article with a blade at an earlier court hearing.

She had 13 previous convictions for 67 offences, including 15 of violence.

In 2000, she was handed a life sentence and jailed for a minimum of three years for slashing an ex-partner across his face and mouth.

"I'm satisfied that in light of your previous convictions, your personality disorder, your use of alcohol and illicit substances and your propensity to carry knives, that you are dangerous and pose a high risk of serious harm to the public," the judge told Savage.

Prosecuting, Anna Midgley said Savage decided to confront her mother after receiving a text message saying that she wanted nothing more to do with her.

In the days before the incident, Savage was described as being unstable.

"Ms Hayton describes bizarre behaviour from the defendant," Miss Midgley said.

"She became fascinated with programmes about murders and serial killers."

Both Savage and Ms Hayton were drinking and taking illicit substances on the journey from Birmingham to Aberdare, the court heard.

Passengers on the train described how Savage began attacking Ms Hayton as she sat in a seat in the train.

"They were extremely frightened by what they saw," Miss Midgley said.

A train guard saw Ms Hayton crawling through the carriage following the incident and called police after seeing blood on windows and a seat.

The train was locked but Savage managed to force the doors open. She was later arrested in a nearby park.

Ms Hayton required 67 superficial sutures and 20 deep sutures for her injuries. She had five separate wounds to her face.

She has been left with facial scarring and a loss of vision in one eye.

Representing Savage, Stephen Thomas said his client had written a letter of remorse to Ms Hayton.

"I have to concede for this defendant that there is a pattern of violent offending," Mr Thomas said.

Speaking after the case, temporary Detective Chief Inspector Jaci Thomas thanked her team for their "outstanding" work on the case.

"This was a shocking and vicious attack, and I am pleased we have been able to bring Lisa Savage to justice," she said.