King Charles has joined forces with Prince Harry’s pal Idris Elba in a new documentary. The King will appear in a new documentary addressing the root causes of knife crime alongside Elba, a Hollywood star, anti-knife activist and the Duke of Sussex’s wedding DJ. In the upcoming BBC documentary entitled “Idris Elba: A Year of Knife Crime”, the monarch will be seen meeting The Wire actor to discuss solutions to the burgeoning problem of knife crime in the UK. Charles, 75, and Elba, 52, will also be joined by some of the youngsters most affected by youth violence. Elba said: “So many people dismi…