When Allied fighters were trapped behind enemy lines during WWII, one branch of military intelligence helped them escape: it was called M19.  The organisation set up clandestine escape routes that zigzagged across Nazi-occupied Europe, enabling soldiers and airmen to make their way back to Britain.  Secret agents and resistance fighters risked their lives and those of their families to hide the men.  Central to M19’s success were figures such as Airey Neave – the first British prisoner to successfully escape…