As part of this series of 'Feedback' on Radio 4(which I'm currently producing)we've set up a regular segment on a radio report or programme that has changed a listener's life. For this couple, radio didn't just alter their life course; it helped them to survive. In 1984, Rob and Eeva John took a long weekend break to Lalibela in the north of Ethiopia, where they were taken hostage by an armed rebel faction. At the time, the world's attention was focused on the famine further south. Nobody knew they were being held - or so they thought. They managed to smuggle a tiny crackly transistor radio through and heard their names mentioned on the BBC World Service. From there, they knew they were safe. This is their story.