A double murderer who became known as the Fishman of Saughton because his work in prison helped in the fight against Third World famine was jailed for six years yesterday for a fire attack at the home of the lover who jilted him.

Alexander Torbet, 59, a former RAF corporal, was originally sentenced to life imprisonment in 1981 for shooting his estranged wife and his father-in-law to death with double-barrelled shotgun.

After his release in July 1994 Torbet formed a relationship with Mrs Christine Forsyth and the couple set up home together in Slammanan, Stirlingshire.

At the High Court in Edinburgh yesterday, Lord Bonomy heard that in October last year Torbet arrived home to find his bags lying on the doorstep. He went to live with his daughter and various attempts at a reconciliation with Mrs Forsyth, 38, were rejected.

On November 11 he sent her flowers for her birthday, but this gesture was ignored and when Torbet arrived at Mrs Forsyth's house after midnight he found her with a 17-year-old boy, clearing up the remains of a party.

Torbet knocked on the window but Mrs Forsyth refused to let him in and he terrified her by threatening to kill himself.

Mrs Forsyth heard a car door slam and saw Torbet drive a short distance down the road before he turned his car round and hurtled through the garden. She heard glass exploding and saw that her garage was ablaze.

Torbet had also set fire to the front passenger seat of his car after spraying it with de-icer.

The emergency services were called but the garage and car inside were totally destroyed.

Torbet had locked the doors of his car and police had to break in to

rescue him.

He was taken to Falkirk Royal Infirmary suffering from smoke inhalation and when police interviewed him he said that the discovery of Mrs Forsyth celebrating in the house with a 17-year-old had caused him to ''blow a fuse.''

His actions caused an estimated #5000 worth of damage.

When Torbet appeared at Falkirk Sheriff Court earlier this month he admitted fireraising charges and committing a breach of the peace at Mrs Forsyth's home by threatening suicide.

Sheriff Albert Sheehan sent the case to the High Court in Edinburgh because he felt that his maximum sentencing power of three years was inadequate.

Yesterday, Mr Hugh Irwin, defence counsel, told Lord Bonomy that while serving his life sentence Torbet had become involved in research into fish breeding.

''He is acknowledged worldwide by experts as having made a very substantial contribution to breeding various types of fish. That has assisted in the fight against famine in Third World countries,'' Mr Irwin told the court.

He claimed that Torbet had suffered a panic attack after the break-up of his relationship with Mrs Forsyth and was in a state of high anxiety when he committed his latest offences. ''He did not intend any harm to befall Mrs Forsyth. He did this as a symbolic gesture.''

The court heard that Torbet had been assessed as posing a moderate risk of future violence in close relationships with women.

Lord Bonomy told him: ''I have no option but to impose a sentence that not only reflects the gravity of the offence but also the risk you pose in certain circumstances to women with whom you might come into contact.''

Torbet will have to serve the sentence imposed yesterday before the parole board looks at whether he should be considered for release in future.

He was a serving RAF corporal when he gunned down wife Ann, 37, and her father John Kidd, 63, in Boddam, near Peterhead in 1981. He had been in the RAF 22 years.

Torbert's wife had left him earlier that day taking the couple's 14-year-old son with her. They had been married for 10 years.

After serving 13 years, he was released on licence and got a job at a butterfly farm in Dalkeith, Midlothian.