Abobeker* is an energetic man from Darfur with a long stride and more lives than a cat. As we speed-walk through Cardiff, he greets numerous Eritrean friends, one of whom he stops to embrace, exclaiming: 'He was with me on the boat to Lampedusa!'

Migrants make a lot of friends, moving around Europe in and out of detention. Abobeker is something of an expert. He has spent time in more than half of Britain's 10 detention centres, and two more in Italy, for over three years in total. He can reel them all off: Four months, four days in Sicily, four months and 17 days in Oakington, nine months in Campsfield - the first time...