Hospital anaesthetist, Dr Thomas Shanks, had kept the fearsome weapon after serving as a doctor in the 1991 Gulf War and used it to appalling effect on the night of May 7 1998.

Driven mad by jealousy after his girlfriend, Vickie Fletcher, left her for another man, he tracked her down in Castleford, Yorkshire, and unleased two devastating bursts of automatic fire, hitting her 10 times in the back as she tried to get away from him,

Shanks, now 57, who had worked with Vickie, a nurse, at Pontefract General Infirmary, was jailed for life at Sheffield Crown Court in April 2000 after being convicted of murder.

The jury rejected his "spurious" diminished responsibility defence and, in March 2003, the Court of Appeal dismissed claims that he was deranged by Gulf War Syndrome at the time.

Today, after reviewing the case at London's Royal Courts of Justice, Mrs Justice Cox ruled Shanks must serve a minimum jail "tariff" of 18 years for his crime.

She said that, had Shanks been sentenced for the first time today - under much tougher sentencing guidelines now in force - his minimum jail term would have been set at more than 30 years.

However, the judge was bound by the rules in force at the time of the killing.

Shanks had been jilted by Ms Fletcher, who began a relationship with a former patient, David Griffin. She was having a drink with Mr Griffin at a Castleford pub when Shanks first confronted her, later returning with an AK47 assault rifle, loaded with a magazine of 21 bullets.

The rifle was in the boot of his car, together with an axe, a sheath knife and a baseball bat. Vickie was walking away from him after a confrontation when he opened fire.

The first burst felled her but, when she managed to rise to her feet, Shanks moved closer and fired a second burst. In total, the nurse was hit by 10 bullets.

Mrs Justice Cox said today that the evidence against Shanks had been "overwhelming" and the judge at his trial had described his defence as "spurious".

He was "angry, jealous and unhappy" about Vickie's rejection of him, and had shown remorse since. He was also suffering "considerable distress" as it was not the first time a woman had left him for another man.

But the judge said that could be no excuse for the carefully planned and premeditated murder.

The worst feature of the case, she added, was that Vickie was trying to walk away from Shanks when he shot her in the back. She was still staggering from the first burst, when he fired the second at closer range.

Mrs Justice Cox said there was also evidence of "several previous occasions" in which Shanks had lost his temper and "manhandled" nurses. He had been disciplied over these incidents and had received a "final warning" before the killing.

The judge rejected arguments by Shanks' lawyers that he was suffering from "a mental disorder" at the time and that merited a cut in his tariff.

She said his good behaviour behind bars painted an "encouraging picture", but was nowhere near exceptional enough to justify a lower tariff than 18 years.

And Mrs Justice Cox told the court: "I am entirely satisfied that, under the present sentencing structure, Shanks would have received a minimum term in excess of 30 years".

After being given credit for almost two years he spent on remand before his conviction, today's ruling means Shanks can apply for parole in April 2016.

However, he will only ever be freed if he can persuade the Parole Board he poses no serious public danger. When, and if, released, he will remain on perpetual "life licence", subject to prison recall if he puts a foot wrong ever again.

Shanks, who was born in Scotland, was arrested in Lennoxtown, Strathclyde, where he had sped by car after the killing. As well as getting life for his former lover's murder, Shanks also received concurrent terms of 12 years and nine years for firearms offences.