Carrie Johnson has spoken of her fear about the release of the serial rapist John Worboys as she made a personal plea to the justice secretary to keep Robert Brown, the killer of Joanna Simpson, behind bars. Johnson, one of Worboy’s victims, said she understood her loved ones’ feeling of being “like sitting ducks”, ahead of Brown’s proposed release in November after serving half of a 24-year sentence. At an event in London to raise awareness for their campaign to prevent Brown’s release from prison, Johnson was accompanied by Boris Johnson and spoke alongside the former justice secretary Robert Buckland, the former home secretary Priti Patel and the shadow minister for domestic violence, Jess Phillips. Carrie Johnson said she was “horrified” by Simpson’s story when she was approached by her friends and family at an event organised by Camilla, the Queen Consort at Buckingham Palace last year. “I remember [them] describing themselves as feeling like sitting ducks, powerless to do anything. And I knew that feeling from my own experience,” she said. “When I found out that taxi cab rapist John Worboys was due to be released much earlier than we thought with no explanation as to why, I remember feeling really scared.” But she added that being part of the successful judicial review that kept Worboys behind bars had taught her “that sometimes against all the odds, you can change things. Your voice doesn’t have to go unheard”. Simpson was bludgeoned to death with a claw hammer by her estranged husband in October 2010, aged 46. Her killer Brown, a former British Airways pilot, carried out the attack while their two young children were in the playroom next door. He then drove with her body in the boot to a patch of land in Windsor Great Park – dropping off his children at the home of his pregnant girlfriend on the way, before burying her in a pre-dug grave. Brown was acquitted of murder by a jury at Reading crown court in May 2011, having admitted manslaughter on the grounds of diminished responsibility. The 59-year-old was sentenced to 24 years for manslaughter and a further two years for an offence of obstructing a coroner in the execution of his duty. But after serving half of his sentence, he is due for automatic early release in November this year. Simpson’s 83-year-old mother, Diana Parkes, said the justice secretary, Dominic Raab, had agreed to meet her on Thursday. He has previously said he will consider pleas to block Brown’s automatic release “very rigorously”. Parkes, who with her husband took on the care of her young grandchildren after their mother was killed, spoke about how the family had been shattered by her death. “There are moments in life you can always recall, and identifying my daughter with my son after Brown bludgeoned her to death is one,” she said. “This was a life-changing tragedy, which altered my whole family’s life for ever.” Simpson’s loved ones handed out 123 yellow roses, her favourite flower, to symbolise the “123 beautiful lives cut short at the hands of a man last year”. Her best friend, Hetti Barkworth-Nanton, gave a chilling account of how Simpson had been killed, warning the audience that her words could be traumatising. She said Simpson’s loved ones tried to believe that Brown was “completely inconsequential“ but added that the reality was that they were terrified. “We her family and friends feel like sitting ducks, but the issue is much wider than that. This is a dangerous man.” Phillips said: “There is no-heat-of-the-moment killing in domestic killing,” and she paid tribute to families such as Simpson’s who were pushing for change. “The level of work that victims of femicide and their families have to do to enact change is something that most people aren’t aware of,” she said. Buckland called on the government to respond to a domestic homicide sentencing review set up while he was justice secretary. “We need a response. And we need an approach from government that does recognise that the law isn’t keeping pace with the reality of coercive control and what builds up to a horrible, final dreadful event of homicide.” A source at the Ministry of Justice said Raab was supportive of the campaign and was minded to use his powers to prevent Brown’s early release from prison but action could only be taken within a few months of the planned release date.