The rocket launched with a loud bang and the sound reverberated through the air. Tim Locks faced an agonising few seconds wait before it reached its target and a cloud of dust and smoke rose from where the building had been.
It was a perfect, direct hit and his comrades let out a huge cheer.
He says bluntly: “I didn’t feel anything towards the people I was killing. I had long since stopped seeing Daesh as human, so I had no empathy for them.
“I may as well have been shooting rubber ducks at the fairground.”
His matter-of-fact response to taking the lives of enemies is something you would expect from a man in the military. After all, they are trained to kill.
But Tim has never been in the army, nor has he had any military training.
He is believed to be the first British civilian without a military background to head to the front line.
Just a few months earlier he had left his comfortable life in Britain to fly to the war-torn region as a volunteer, to fight against IS with a Kurdish militia group.
The 39-year-old sold everything he owned, including his home, and shut down his construction business after watching news reports of the atrocities carried out by IS terrorists.
And now he tells his astonishing journey from builder to soldier in detail for the first time in his book, Fighting ISIS.
But, speaking in a London restaurant, he is very quick to downplay any talk of heroism.
He says: “I’m just a guy who was lucky enough to get out there and do his tiny part.”
It was August 2014 when Tim made the big decision to go. “I thought, ‘This is the worst thing that’s happening in the world and everyone says they’re appalled but they don’t do anything about it.’
“I started to question myself. I’m saying that people should be doing stuff but what am I doing about it?”
At the time, Tim, who has also worked as a nightclub bouncer and prison officer, ran his construction business and had built himself the “perfect bachelor pad”, with a swimming pool and bar.
But suddenly all those material possessions became meaningless. Apart from a select few friends, no one knew of his plans – not even his parents.
“I didn’t know whether I would be stopped at the airport if word got out about why I was going, so I was careful who I told,” Tim says.
“Friends knew my house was on the market and my cover story was that I was going to Turkey, as I’ve spent a lot of time out there.”
His spare bedroom became his kit room as he bought body armour and other equipment online. “It’s amazing what you can buy on eBay when you know where to look,” he smiles.
Tim also took a basic firearms training course but it “barely scratched the surface”.
It was only after his house had sold for a “six-figure sum” and his plane ticket had been bought that he broke the news to his family.
Tim says: “They tried in vain to talk me out of it, using arguments that ranged from the fact I was sure to be prosecuted when I wanted to get back into the UK to the fact that my size made me a big target. But my mind was totally made up.”
He flew out to the city of Sulaymaniyah, in Iraqi Kurdistan, in February 2015, to join the Christian militia called Dwekh Nawsha, which translates as the self-sacrificers.
As soon as he arrived, he was told that IS had put a £100,000 bounty on the heads of any Westerners in the area.
Tim says: “I wasn’t scared. It’s more propaganda. They are all smoke and mirrors.”
He poured the money he had brought into stocking up on weapons, including a Glock and an AK-47 rifle he bought on the black market.
And a few months later, Tim learnt just how real the terror group’s threat was when, after finally getting his paperwork sorted, he went to the front line for the first time.
He was on the roof of a building occupied by the Peshmerga, the Kurdish defence force. He recalls: “I could see the famous water tower and the Daesh flag. It seemed they were aiming for our building and a spotter was helping adjust the angle of the weapon one click at a time to home in on their target – us.
“I looked around and stopped for a few moments to consider the options. As a volunteer fighter, I had no army commander to tell me what to do.
“With no previous military experience it was all about using common sense and keeping level-headed.”
Going with his gut instinct, Tim ran down the stairs, before diving into a nearby trench – much to the amusement of his Scottish comrade JP, who is ex-Army.
Tim laughs: “He said I was the first civilian he’d seen running towards mortar fire. He jokingly said he didn’t know if I was crazy or stupid.
“I don’t think I’d describe myself as either. I went out to destroy Daesh and the best place to do that is on the front line. If you run away from them there’s no point going out there in the first place.”
Tim also discovered that war, Kurdish style, was not what he expected.
“There were some Pesh guys in the trench and they were more interested in taking selfies,” he explains. “They had been there for months getting mortared and shot at every day.
“Suddenly there’s a Western volunteer in their trench and it’s a good time for a cup of tea and a selfie.”
A year ago, Tim returned to the UK for a brief break, before going back out to Kurdistan in November.
This time he joined IDET, a volunteer unit of western veterans, to help clear villages and to be closer to the action.
There were a few close calls, including narrowly escaping being blown up by an IED and his vehicle breaking down during a mortar attack.
“We had a sing-song as mortars were dropping around us,” he says. “I think the American guy with us found our reaction a little difficult to comprehend. But panicking isn’t going to help the situation.”
Life on the front line also had its low points, particularly last Christmas. “I did miss my family and friends,” Tim admits. “Most of us put it out of our mind. One of the boys bought some Christmas hats and I put up posters of Cheryl Cole to try to brighten up my room.”
Tim made a photo of three-year-old Syrian boy Aylan Kurdi, whose body was washed up on a Turkish beach in 2015, his phone screensaver “as a reminder”.
And he says the harrowing stories he heard kept him going. “I met people who have had to leave Syria and Iraq because Daesh have just rolled in and taken over,” he says. “Of course it affects you.”
Exhausted and penniless, Tim eventually returned to the UK in March. Each time he has come home he has been questioned about his activities in Kurdistan but he says that the authorities were satisfied with his explanations. Now, however, he has nowhere to live.
He says: “People have been very kind and helped me out. It’s been very humbling.”
And he believes the threat from IS is just as real for him on home soil.
“ Daesh are in the UK – that’s definite,” he says. “I’m aware of being a target so I take sensible precautions.”
Tim, who will put the profits from his book into thr fight against IS, says he has no regrets and is planning to return to Kurdistan in September.
He says: “I’ll be out there for my 40th birthday, destroying some Daesh hopefully – that will be a good birthday present.”