Eritrea has been described as one of the most secretive states in the world. Every year, thousands of people flee indefinite military service and arbitrary imprisonment. But now, for the first time in around ten years, BBC News has been allowed to film inside the country. The authorities want to show off some positive news - they say child mortality is falling, maternal health is improving, and malaria has almost been wiped out. But alongside the gleaming hospitals on show, will Our World's Yalda Hakim gets a glimpse of why so many young Eritreans will risk everything to leave the country.