TWO sons of a multi-millionaire killer who stabbed his wife in the midst of their bitter divorce are now suing him for £1.5 million.

In a "unique and troubling" case, Ben and Nicholas Workman say their murderer dad, Ian Workman, 63, would have had to hand over half his fortune to their mother, Susan, had he not killed her.

And if he is allowed to keep the cash, he will have "profited" from murdering her with a single stab wound to the heart, the brothers' lawyers argue.

But Workman, who is serving a life sentence, is defending himself from his prison cell, insisting he didn't kill his wife for the money.

He is also said to have given away almost his entire fortune to his eldest son, Grant, 28, who the court heard is standing by him.

The car dealer, said to have been worth about £3.3 million, killed his wife following a row at the family home in Edgworth, near Bolton.

He "stabbed her through the heart with a large kitchen knife" in April 2011, his sons' QC, Stephen Killalea, told London's Civil Appeal Court.

Workman snapped as the estranged couple rowed over the financial fallout from their divorce, he added.

Aged 55 when she died, Mrs Workman had been claiming a divorce payout of around £1.5 million from her ex.

But the cash stayed in his coffers after he was convicted of her murder at Preston Crown Court in December 2011.

Workman says he has been treated "unfairly and oppressively" by Ben, 27, and Nicholas, 23, but they are determined he should not profit from their mother's murder.

Backing their claim is Susan Workman's sister, Carol Forrester, who is representing her murdered sibling's estate.

Workman watched the case via live video link from jail as his lawyers insisted he had been given no fair chance to defend himself.

And his barrister, Katherine McQuail, said his oldest son, Grant, 28, has "stuck by" his dad.

Nicholas and Ben's legal team argue their father "would have been ordered to pay his wife some £1.5m had the financial proceedings gone ahead".

And they are now claiming every penny Workman would have had to shell out to their mother had she lived - plus legal costs of around £500,000.

The brothers' case reached the Appeal Court as Workman challenged a judgment for £1,503,579 that was entered against him in 2013.

As part of an asset-freezing injunction, Workman had been ordered to disclose his assets worldwide.

But Mr Killalea said he made "no attempt at all" to comply with the order and, as a result, was barred from defending his sons' claim.

The QC also claimed Workman had "voluntarily dissipated virtually all his assets" to Grant.

Workman's obstruction of the legal process had led to "horrendous delays" and caused "intense emotional strain" to Ben and Nicholas, he added.

And his behaviour had deepened the trauma already caused by their mother's murder.

But Miss McQuail urged the Appeal Court to give Workman a fair chance to defend himself against his sons' claim.

Denying that a "profit motive" lay behind the murder, she said Workman was "in temper" when he killed his wife at the climax of a "bitter dispute".

He and his victim had been married for 35 years before their split, the court heard.

During his trial, Workman insisted he acted in self defence after his wife came at him with a kitchen knife and that she was fatally injured during the struggle.

However, jurors disbelieved him and his conviction challenge was turned down by the Criminal Appeal Court in 2014.

At his murder trial the court heard poignant extracts from Susan Workman's diary - with the last entry penned just instants before the killing.

The log - titled "Sue's Memories" - recorded how her ex stormed into the house to retrieve his "clothes and jumpers".

Workman briefly stroked the family dog as he was about to leave, the diary notes, but then launched a torrent of screaming expletives at Mrs Workman.

Her last unfinished line read simply, "standing, staring at me acro..."

After Workman's trial, Ben and Nicholas put their names to a family statement welcoming "this man"s conviction."

"Sue did not deserve to have her life ended this way for greed and money," they said.

Lord Justice McCombe, Lady Justice Sharp and Lady Justice Thirlwall have now reserved their decision on Workman's appeal.