I'm an addict. I used heroine and crack cocaine for years, and it led to a lot of criminal behaviour. Over the years I've been in and out of prison numerous times and served a total of 27 years. I came out of prison in December last year for the last time.
During my most recent prison sentence I was taken aback by how few people were using the usual drugs of choice in prison - heroin and crack. It's all spice in prison now. It's only a very few hard core users who persevere with heroine or crack. With spice you're out of it all day and it doesn't show up on drug tests and it's easily available. On the wings I was on, about half the people were using spice.
The impact of spice on prison life is so much worse than anything I saw in any of my previous sentences. I call it the green crack. I went from smoking a couple of joints a day to quickly smoking significantly more, because the tolerance goes up so quickly.
I was lucky and never had any of the frightening effects spice can have, but I saw others who used it have 'spice attacks'. It's like they were having heart attacks, not knowing where they were, collapsing. Men would smoke half a gram in one go. They'd wander out of the cell, and the next thing they'd be on the floor or in health care. A lot would call for their mums.
I saw a lot of violence too. It was a nightmare - hands being slammed in prison doors, fingers being broken over 20 quid's worth of spice. There were serious assaults where large amounts of money were owed. It was intrusive and violent. And it was always around money.
I don't know what the solution is for prisons, but I do know that it's possible for prisoners to get clean from spice.
I was transferred to HMP Rochester towards the end of my sentence, where a drug worker from the charity RAPt (Rehabilitation for Addicted Prisoners Trust) encouraged me to try one of the RAPt drug treatment programmes.
It took me a while to really buy into it, but after a while I began to work really hard at the programme and I passed with flying colours. But this was only the start of my rehabilitation. I was released from prison soon after and RAPt arranged for me to attend The Bridges Residential Rehabilitation Centre in Hull. I started there on the day I left prison in December 2014 and I completed the programme in April 2015.
When I look back on all that time in prison I can feel my shame rising as I remember that my Dad died knowing that his youngest son was a 'junkie', in and out of prison. He had tried so many times to help me and he never gave up hope. I lost my Mum in August 2014 and I'm still working through the fact that I'll never be able to look her in the eye and say how sorry I am that I wasn't there when she needed me most.
I've been free from drugs since September 2014, when I first started the RAPt programme at Rochester prison. I'm also free from crime. It's not been easy, getting my life back on track. I'm now living in my own flat in Hull, and later this year I'm looking forward to getting back into work. For me and my parents, I just want to be the nice man that they could always see. I don't ever want to go back to prison, or the life I had before. And I hope that others who are in the place I was in can get the help they need to turn their lives around too.
Dan was supported by an intensive rehabilitation treatment programme from charity RAPt (Rehabilitation for Addicted Prisoners Trust), who have released a briefing and new statistics on the use of new psychoactive substances in prisons. For more information visit www.rapt.org.uk or follow the news story at www.bbc.co.uk/newsbeat