In ‘Not Forgotten: Shot at Dawn’ Ian Hislop, whose grandfather fought in WWI, looks at the lives of six soldiers executed during the war.  Through their stories, he asks, is it dangerous to try to rewrite history?  And he poses an uncomfortable question: Are some of these men, under the strict military law of the time, really deserving of a pardon, or is it sentimental to view them all as innocent victims?