Johnson, 64, was ordered to serve a minimum of 26 years in prison after he savagely beat ex-girlfriend Angela Best with a claw hammer before throttling her with her dressing-gown cord. 

Johnson flew into a rage after the mother-of-four began a new relationship. 

Ms Best, 51, had learnt of Johnson’s past only weeks earlier, when she found letters at his home and confronted him. 

Johnson’s history of violence against women included convictions for manslaughter after killing his wife by throwing her off a balcony in 1981 and strangling another partner in 1993. 

Johnson met Ms Best while on day release from a secure mental hospital.  

After carrying out the murder at his home in Islington, north London, the garage worker threw himself in front of a train. 

He is now wheelchair-bound after suffering severe injuries, including losing both his arms. 

Sentencing him at the Old Bailey today, Judge Richard Marks QC said: “The attack by you on Angela Best was sustained, vicious and utterly brutal. 

“She suffered an unimaginably terrible death. 

“Such repeated offending, resulting in three separate court cases, must be almost unprecedented.”  

After the hearing Ms Best’s sister Lorraine Jones accused Johnson of attempting to “play the system” to get away with murder. 

She said: “This convicted murderer tried to play the system as he has successfully done before. 

“He claimed diminished responsibility as the cause for his murderous actions. 

“This time he has eventually pleaded guilty to murder 12 months since his arrest after subjecting our family to unnecessary additional trauma.” 

In 1981 Johnson was found guilty by reason of “provocation” of killing his wife Yvonne Johnson by pushing her off the balcony of their ninth-floor flat in Wolverhampton.  

Then, in 1993, two years before meeting Ms Best, he was convicted of strangling his partner Yvonne Bennett at their home in London before trying to hang himself. 

Jamaican national Johnson was last seen by a social worker and psychiatrist on December 8, 2016, just seven days before the murder. 

He was not found to be depressed and continued to deny being in a relationship. 

For Johnson, Annette Henry QC said her client was likely to die behind bars. 

She said: “He does not wish to be alive. 

“He hates himself for what happened. 

“We recognise the devastation felt by the family members.”