The man who spoke to me on the phone from Morton Hall detention centre in Lincolnshire asked me not to use his name. ‘At 10.30,’ he said, ‘they put us on a bus and took us to a private airfield in Doncaster although they were fighting for our case outside. I see police. I see dogs. It was like hell. We were watching other detainees going inside the plane. We were shaking, thinking any moment it’s going to be us.’

In August 2012, Fadi Mansour, a 28-year-old law student from Homs, left Syria to avoid conscription. ‘I had to do my military service before the war started; after the war they called me to fight in the reserve army, so I escaped,’ he wrote to me yesterday. He told Amnesty International that he went first to Lebanon, where he was kidnapped and held to ransom. After his release he felt unsafe; in early 2015 he came to Turkey. He flew to Malaysia but was denied entry and sent back to Istanbul. ‘They caught me in the airport,’ Mansour said. ‘I asked for asylum here. But they rejected my request.’ This was on 15 March 2015. Since then Mansour has been detained at Istanbul's Atatürk Airport. He is living in the ‘Problematic Passengers Room’. It has no natural light and no beds. The electric lights are kept on around the clock. ‘Sometimes they let me go outside the room for one or two hours,’ he told me. ‘But nothing is different between here and outside.’

When you go to see someone at Harmondsworth Detention Centre near Heathrow, you sit in a waiting room until your ticket is called and you are led into the large visiting room. After a while, the person you are there to visit enters through a door on the other side. The waiting room and visiting room are decorated with photographs printed onto canvas. The photos are the stock kind you might get on the desktop of a Windows PC: deserts, beaches, lush forests, drops of water, lands of mineral richness. They appeared after Mitie took over running the centre from GEO (both are private companies). Artwork by detainees used to decorate the walls, but now those pictures are stacked up in the corner.