Govia Thameslink Railway (GTR) will take a case to the High Court in London against the drivers' union Aslef.
Jury Returns Verdict on Lesley Dunford
A woman has been jailed for seven years after being found guilty of smothering her three-year-old daughter to death, six months after her baby son also died.
A judge said Lesley Dunford, 33, went from "carer to killer'' when she ended the life of Lucy Dunford.
Dunford inflicted fatal injuries on Lucy, who was found with bruising under her skin around her shoulders and neck.
The toddler also had a cut above her left eyebrow which jurors heard could have been caused by hitting a hard surface such as the headboard of a bed.
Dunford, of Rydal Mews, Windermere Close, Exeter, had denied murdering Lucy at the former family home in Pelwood Road, Camber, near Rye, East Sussex, on February 2, 2004.
Jurors at Lewes Crown Court found her guilty of manslaughter but cleared her of murder.
Lucy's death occurred on the same day that Dunford's husband, Wayne, 54, had returned to work following a 19-month spell of unemployment.
It also happened six months after the death of their seven-month-old son Harley, who was found dead in his cot at their home on August 3 2003.
Dunford was arrested just two days after Lucy's death but the Crown Prosecution Service decided not to prosecute her.
An inquest into Lucy's death was held in February 2009 but the coroner adjourned the hearing for further examination of the case.
Five months later, Dunford was arrested on suspicion of murder.
As Mr Dunford comforted his wife, he told her: "We have been expecting this. We knew this was coming. It has been a long time.''
Detective Constable Janice Dempsey, of Sussex Police, also said Dunford told her as she was getting dressed: "I have been waiting for this to happen.''
Later, in police interview, Dunford denied killing Lucy and said she had never struggled as a mother. She told officers: ``I did not kill her. I have no reason to kill her.''
The jury heard that Dunford did not try to resuscitate her daughter when she found her because she was too frightened to touch her.
Instead she phoned a friend, the Reverend Lucy Murdoch, who came round. It was only when she arrived at the family home that an ambulance was called.
Lucy was rushed to a waiting air ambulance and she was taken to the Conquest Hospital in St Leonards-on-Sea. One of the paramedics noticed blue marks on Lucy's neck as he tried to revive her.
Lucy was intubated on the way to hospital and that was when she vomited. Despite efforts to resuscitate her, Lucy was pronounced dead at 4.30pm.
Three post-mortem examinations were carried out on the youngster and each found she died from asphyxia caused by the forced blockage of her airways.
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