Like hundreds of thousands of east Europeans, Vassili Zen, a Ukrainian telecoms engineer, moved to Spain a few years ago to work in the booming construction sector.

Mr Zen cuts slate to build weekend homes in the mountains north of Madrid. It is back-breaking work but he does not complain. He earns about €1,000 ($1,480, £750) a month – much more than he was paid back home fixing telephones – and significantly more when he works weekends. Mr Zen says he has not taken a holiday for five years.