"These people have been in the UK 30 years. Some were born here. They've Yorkshire accents, cockney accents. They're being sent back to countries where they've got no ties whatsoever. They will riot."
Thousands of men and women live in Britain's immigration detention centres. They have committed no crime.They are often locked up for years, never knowing when they'll be let out. Theirs is a grey world – neither legal nor illegal, kept away from the public or the press, constantly at risk of being removed.
They are monitored by guards, sometimes on loan from the prison service, sometimes employed by private contractors. These men and women keep quiet. They're prevented from talking about their work under the Official Secrets Act. But they are the front line in Britain's immigration system. And they don't always like what they see.
This is the story of a man we'll call Mark. That's not his real name. I've removed references to specific institutions to protect his identity.
He is not a bleeding heart. Over the course of our conversation he will say several things which would make a liberal blanch. But he sees the daily reality of Britain's immigration system. He sees fathers torn from their families. He sees a centralised decision-making system making baffling choices without regard for sense or compassion. He is not a bleeding heart, but he is haunted too.
"I wish I'd never gone there," he says of the centre he works in. "It breaks your heart. Back in the prison service, it was clear cut. I had to look after them. If they spat in my face, I hit them with my stick. Here it's all grey. Some people get bailed, some get released, some get sent to countries they've never been to their whole life.
"I have opinions. We all do. I don't know if everyone is of the same opinion as me, but we talk and in general people are on the same lines.
"They send the wrong people back. You can't allow everyone to stay. It would be fantastic if that was the case but people are sent back and rightly so. Thing is, they don't seem to get it right. They don't have compassion. They don't believe a word a detainee says. No-one could possibly be saying the truth, they think."
Mark was working a different career when the break-up of his marriage encouraged him to start again in the prison service. "I have worked in some very, very nasty places in my time," he says. "At first it was scary and horrible and I almost immediately regretted changing careers to do it."
But there were good sides. Prison work is relatively well paid and it offers guards – at least before staff cuts slashed the service - the chance to help prisoners turn a new leaf. "We're dealing with people's lives here," Mark says. "This is serious shit. We can't afford to get it wrong, we can't use a rubber, we can't erase it and start again."
He adds: "I joined the job not to put people away, but to make things better. I was a personal officer to six or seven prisoners. I got right involved with that. They told me about their families, their crimes, their children, what their problems were. I could put them in the right direction to get the help they needed."
Then Mark moved to work in a detention centre and everything changed.
"There's nothing I can do to help. Absolutely nothing. It's all about the Home Office. They set the rules and we just implement them. In prison you can do a report which might lead to them getting early release or getting tagged or something. There's things you can do to help turn around that person's life. In detention, there's nothing. All I can do is open and close doors and help them use the fax machines."
Mark has gone from guarding criminals to average members of the public and he can feel the difference.
"Certain places in prison are flash points," he says. "One is reception. They arrive and the first thing they see is load of hairy-arsed screws saying they need to strip, that they can't keep their clothes. That can be a real flash point for violence. In the detention centre, they're like: 'Thank you, good evening.' That sort of thing. I've gotten used to it now but it took a while.
"One minute they're studying in Sheffield, the next they're in detention. But because they're not criminals, they actually deal with it better.
"I used to be able to count on one hand the number of times a prisoner said good morning to me whereas now 200 will say that. They understand we're not part of the problem. The problem is immigration. That's not done by people wearing my uniform, it's done by faceless people wearing a suit.
"It's very frustrating. It's difficult to watch their families come in on visits. You wobble a bit more emotionally."
Mark's detention centre, as well as many others, contains many former foreign prisoners who are transferred ahead of removal. They are mixed in with the normal population. For many of them, detention is practically a holiday camp compared to prison. They are given their belongings back. They can socialise in each other's rooms. They can move around outside their cell freely. But for many of the normal members of the public who suddenly find themselves in detention, the presence of former prisoners can make the experience tougher and more traumatic.
It also makes it much harder to maintain security. Riots and protests are becoming more common, which is not surprising considering the fact inmates are being imprisoned without having committed a crime, for an indeterminate amount of time. The addition of former prisoners to institutions brimming with pent-up frustrations and feelings of injustice has proved explosive. Complaints are made, but the Home Office refuses to change its policy.
Working in detention allows guards to see the reality of the system up close. And they do not always like what they see.
"This lad got sent to Pakistan," Mark says. "He had a broad Yorkshire accent, he worked for a living, but he didn't have the paperwork to stay. That's not good – I'm not defending it. But imagine it. He was married. He had four small children - beautiful children. They were polite and respectful. They came to see their dad every Sunday. And we sent him to Pakistan.
"We've created a woman, single with four kids, who'll now have to rely on the state. I mean, she's going to find it bloody hard to work with four kids and the bread-winner, the provider, has been shipped thousands of miles away. Those are four kids that don't get to see their dad again."
He goes on: "These are people who've made lives here. Maybe they shouldn't have in the first place. But they are people who own businesses, who have shops, who have been here for many years, who have ties to the local community, who have a mother and father here legitimately but for whatever reason the son isn't allowed to be here - and off he goes back to Jamaica or whatever.
"And then there's people who have literally come on the back of a lorry and they get bailed. It happens on a regular basis. I'm not privy to the reason why that happened and there might be a legitimate reason but I'm fucked if I can think of one."
It's hard to report on immigration detention centres. The public barely knows they exist. They are hidden away, in places you would never otherwise go to. For those detained in them, they are an endless nightmare. But those who work in them are haunted too.
Mark still works at a detention centre. This is his immigrant story.