The signatories, who include chief constables from across the UK, say every "lawful option" should be explored to prevent the release of PC Harper’s killers. In a statement released by Gloucestershire Constabulary, Ms Blyth and her fellow police chiefs requested three actions from the Government. The second request is for the Government to introduce new public protection measures to cover the most serious offenders when considering early release schemes in the future. Metropolitan Police Commissioner Sir Mark Rowley, Greater Manchester Chief Constable Stephen Watson, and National Crime Agency director general Graeme Biggar also signed the letter. Although recent changes prevent rapists and paedophiles from being released early, they do not apply to the men convicted of PC Harper’s manslaughter.