Jeremy Vine and Tina Daheley are once again live from the location of one of the UK's biggest unsolved cases. They also have the very latest developments on last week's appeals. This edition also features a special investigation into the recent spike in knife crime, particularly involving teenagers. Alison Cope, whose son Joshua was stabbed to death in 2013, explores why so many of Britain's youngsters are arming themselves with knives. Plus there is the inside story of how detectives caught a schoolboy killer. Double murderer James Fairweather was just 15 when he stabbed and slashed father-of-five James Attfield more than 100 times in Colchester in March 2014. Three months later, Fairweather went on to murder 31-year-old student Nahid Almanea, who was found stabbed to death on her route to university. The Crimewatch Update programme has been replaced with a new live digital platform linked to the show's website, which keeps audiences up to date with developments on the cases.