This is of course pure politics, simply playing to the base, as Boris demands the end of early release for prisoners after serving half their sentence:
Prisoners will no longer be automatically released early under plans to be set out by Boris Johnson this week, The Telegraph can disclose. The Prime Minister will pledge to end the automatic release of serious criminals who are currently freed after serving half of their sentence. He will press for a tougher stance on sentencing at a roundtable meeting in No 10 on Monday with police chiefs, prosecutors, former judges, courts administrators and prison bosses.