Former Prime Minister Boris Johnson has supported his wife Carrie in backing a Sulby mother’s campaign to keep a killer behind bars.

Carrie Johnson said releasing Robert Brown halfway through his 26-year sentence for manslaughter would signal ‘a real failure in our system’.

Robert Brown, 59, battered estranged wife Joanna Simpson to death with a claw hammer in 2010. He is due for automatic release in November.

Joanna Brown (Simpson)

Joanna grew up in the Isle of Man and her mother Diana Parkes, who lives in Sulby, fears that her daughter’s killer will return to the island if he is freed.

Mrs Parkes is leading a campaign to urge ministers to block Brown’s release on parole.

She was joined at a campaign launch in Westminster this week by Mrs Johnson together with her husband, as well as former Home Secretary Priti Patel and former Justice Secretary Robert Buckland.

Speaking to the audience, Mrs Johnson described how she had experienced a ‘similar injustice’ over black cab rapist John Worboys.

Diana Parkes ( )

Worboys drugged her when she was only 19 after he picked her up in his black cab following a night out with friends.

Mrs Johnson blacked out and says she does not know what happened, but does not believe she was assaulted.

She was one of 14 women to give evidence against him in court, and later waived her right to anonymity to campaign against his proposed release.

Mrs Johnson said Joanna’s family had felt powerless to do anything .

She said: ‘I knew that feeling from my own experience, when I found out that taxi cab rapist, John Worboys, was due to be released from prison much earlier than expected, with no explanation as to why.

‘It was a similar injustice, a similar circumstance where the law was badly letting victims down and failing to do its job to protect women.’

Joanna and her BA pilot husband were going through an acrimonious divorce when he carried out the brutal attack at the marital home in Ascot, Berkshire, in October 2010 – within earshot of their children playing in the TV room nearby.

Brown put her lifeless body in the boot of his car, pulled out the CCTV and telephone cables, told the children to get into the car and drove to his pregnant girlfriend’s home and left them with her.

He then dumped Joanna’s body in a grave he had spent months digging in Windsor Great Park.

Following a two-week trial, a jury acquitted Brown of murder – a decision with which Joanna’s family are still struggling to come to terms.

After her daughter’s death Mrs Parkes took Joanna’s two children Katie and Alex, then aged nine and 10, into her care.

Mrs Parkes told the Isle of Man Examiner last year: ‘We all believe this guy is a psychopath. He’s really, really dangerous. We are frightened he will come here. He’s shown no remorse whatsoever.’

Read here how Mrs Parkes inspired Camilla.

Read here our story from last year about Mrs Parkes' fears about Brown's release.