A woman who was already in jail for killing her daughter has been sentenced to 13 years after admitting she murdered her baby son.
Lesley Dunford, 37, smothered seven-month-old Harley Dunford in his cot on 27 August 2003. Her three-year-old daughter Lucy died in similar circumstances six months later.
Harley's death was not treated as suspicious until she admitted the killing to prison staff in 2014, while serving seven years for the manslaughter of her daughter.
The Old Bailey heard that Dunford, who pleaded guilty to murder, was "riddled with guilt".
Jailing her for a minimum of 13 years, Mr Justice Baker said: "The reality is, had you not confessed to killing Harley whilst in custody, it is highly likely there would not have been a police investigation into his death and you would not have faced prosecution for murder."
Dunford killed Harley at the three-bedroom home near Hastings which she shared with her husband Wayne.
Until Dunford's confession at Drake Hall women's prison in Staffordshire in June 2014, Harley's death had been put down to staphylococcal pneumonia and no action was taken.
Lucy died in "very similar circumstances" in 2004, the court heard.
But it was not until a coroner expressed his concern at Lucy's 2009 inquest that the decision not to prosecute over her death was reconsidered.
The medical evidence was reviewed and it was found that Lucy had died from asphyxiation, the court heard.
In June 2012, Dunford was jailed for seven years after being found guilty of Lucy's manslaughter at Lewes Crown Court.
It was while she was serving her sentence that she admitted involvement in both deaths to prison staff, saying she was "riddled with guilt".
She told officers that she had been having "flashbacks and nightmares".
In a written confession, she said: "I remember the day very clearly, the time I put Harley back to bed at 9am, after I had given him his breakfast. I was settling him down in his cot. I put him on his tummy and put his dummy in.
"But then something clicked in my head and I went back into the room walked over to his cot and pushed his face into the mattress until he stopped breathing.
"And then I put his head to the side and noticed there was blood and foam coming out of his nose. That's when I knew I had hurt him and I don't know why I had done it."
Her husband is in the process of divorcing her but says he has forgiven her and "wishes her well in future".