Migration is high on the political agenda in countries across Europe, as the number of asylum seekers rises once more. As well as those who risk life and limb on flimsy boats in the Mediterranean, thousands more come via the Balkans, many of them through Turkey and across the border into Bulgaria. They don’t stay there long. Their preferred destinations are further west, Germany perhaps or Britain. And while the migrants’ stories have become well-known in recent years, we hear relatively little from the people who enable their journeys, the people smugglers.

For Assignment, Nick Thorpe has been to the north-west of Bulgaria, where it meets Serbia to the west and Romania across the Danube to the north. There he meets two men who worked as drivers for a smuggling organisation, shuttling migrants from Sofia, the capital, to the border.