Recently convicted of murder of teenage actor who starred in new ` ` Harry Potter '' film . Karl Bishop , 24 , attacked Rob Knox with two knives in southeast London last May . Knife crime in London is political hot topic due to reports of recent murders .
Man convicted of murder of teenage actor who starred in new `` Harry Potter '' film . Karl Bishop , 22 , attacked Rob Knox with 2 knives in southeast London last May . Knife crime in Britain is political hot topic due to spate of recent killings .