A triple killer tried to “play the system” to escape a murder conviction for killing his ex-partner, having avoided murder convictions twice before, the sister of his latest victim has said.

Theodore Johnson, 64, who was convicted of killing two previous partners, was jailed for a minimum of 26 years on Friday for murdering his ex-girlfriend Angela Best after she met another man.

He was sentenced at the Old Bailey on Friday after pleading guilty on the first day of his trial – having earlier claimed diminished responsibility – to murdering the mother-of-four and grandmother with a claw hammer.

In 1981, he was found guilty of manslaughter rather than murder by reason of “provocation” after killing his wife Yvonne Johnson by pushing her off the ninth-floor balcony of their home in Wolverhampton.

Then, in 1993, a couple of years before meeting Best, he pleaded guilty to manslaughter on the grounds of diminished responsibility, after strangling his common law wife Yvonne Bennett with a belt at their home in London before trying to hang himself.

He was found to be suffering from depression and a personality disorder and was sent to a secure hospital indefinitely, having killed her while their baby daughter slept nearby.

After his sentence on Friday, Best’s family gathered to give a statement before the press, in which her sister Lorraine Jones said: “This convicted murderer tried to play the system as he has successfully done twice before. He used diminished responsibility as the cause for his murderous actions.

“This time however, he eventually pleaded guilty to murder after 12 months since his arrest and subjecting our family to unnecessary, additional trauma. He has shown in all cases he was clearly of sound mind.”

She called her sister “the heartbeat of our family” who was “an inspiration to everyone that came in contact with her”.

Best and Johnson had broken up but she went to his Islington home on December 15, 2016, to help him with an appointment at the Jamaican Embassy over his documents.

People wept in the court’s public gallery as the sustained attack he carried out there was described. Johnson attacked her with the claw hammer and throttled her with her leopard print dressing gown belt.

Judge Richard Marks QC said: “The attack by you on Angela Best was sustained, vicious and utterly brutal. She suffered an unimaginably terrible death.”

Jones said Johnson had known “exactly what he was doing when he planned and executed the horrible murder of our beautiful beloved Angela”.

She added: “Despite our family’s immense pain and suffering our hearts and thoughts go out to the other two families who have also suffered as a result of his evil and calculated actions.” 

After his fatal attack on Best, the garage worker threw himself in front of an express train, which resulted in him losing his right arm and left hand.

He now uses a wheelchair.

Police discovered Best’s body when they called at Johnson’s flat to find his family after the incident at Cheshunt railway station.

Johnson had met Best while on day release from a secure mental hospital following his 1993 conviction.

Johnson was conditionally discharged from the secure mental health facility in 1997.

One of the conditions of Johnson’s release was that he was required to tell authorities if he entered into a relationship but he persistently failed to declare his relationship with Best, the Old Bailey heard.

Johnson’s relationship with her ended in 2016 when she met someone else.

Annette Henry QC, defending, 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.”

She added the mental health tribunal’s condition on Johnson’s release was flawed as it relied on “self reporting” any new relationship.

She said: “This was a dilemma and the tribunal found it was fraught with difficulty in trying to monitor.”

Judge Marks said: “This was a deception that must have gone on for something like 15 years.”

Camden and Islington NHS trust, which provided care to Johnson, is to commission an independent report into its contact with Johnson who it began providing care for in December 2004.

Lorraine Jones’ full statement following sentencing

“Angela was an inspiration to everyone that came in contact with her. She was kind, loving and very, very caring. She was always smiling and radiant.

“It was never any trouble for Angela to offer any help and support to anyone who needed it because that was her nature. 

“Angela has children and grandchildren who she doted on and loved dearly. Angela has parents, brothers, sisters, aunts, uncles, cousins and other extended family and friends. All loved her dearly.

“She was the heartbeat of our family. This convicted murderer tried to play the system as he has successfully done twice before. He used diminished responsibility as the cause for his murderous actions.

“This time however, he eventually pleaded guilty to murder after 12 months since his arrest and subjecting our family to unnecessary, additional trauma. He has shown in all cases he was clearly of sound mind.

“He knew exactly what he was doing when he planned and executed the horrible murder of our beautiful beloved Angela. 

“Despite our family’s immense pain and suffering our hearts and thoughts go out to the other two families who have also suffered as a result of his evil and calculated actions.

“We would like to thank the police, the prosecution team and all those who have sent us their kind thoughts. The facts of the case have been reported. Our family have no further comment, we therefore ask the press to respect our privacy at this incredibly difficult time to allow us to grieve.”