Warning: This article contains details of violent deaths that some readers may find distressing Helena is looking at an old photo on her phone of nine teenage girls smiling at the camera on their last day of secondary school. "Leaving school with all their hopes and dreams," she says. "Two women on that photo have been murdered by men." One is her daughter, Isobella Knight - killed at home last year by her husband, Paul, as their two young girls lay sleeping in their bedroom. The other is Sabina Nessa, murdered by a stranger almost five years ago as she walked through a park in London. The two had been friends at the Bedfordshire comprehensive they attended together. Helena describes violence against women as an "epidemic". Ministers have described a "national emergency" and the UK government has pledged to halve violence against women and girls within a decade.…