The first time you see a child hunched over a sewing machine in a hot, airless factory will never leave you. The boy, no more than 11 or 12, peeked up at me with just the trace of a smile before he dipped his head down again, and got back to work. It felt like a punch to the gut.
I'd been told that child labour was endemic in Turkey, but I wasn't prepared for the reality of it. Or the scale of it. One basement workshop was almost entirely staffed with children, many of whom couldn't have been more than seven or eight years old, the very picture of Dickensian misery.
I was in Istanbul investigating allegations that Syrian refugees and children are being exploited by the garment industry. And specifically that many are working on clothes destined for our high street.
This undercover investigation was unusually tricky. Not only is secret filming illegal in Turkey, but half way through our investigation a state of emergency was declared in the country. This meant that we were routinely stopped and questioned by police and our secret filming equipment had to be kept out of sight. Despite this, finding Syrian refugees and children working on branded goods for our shops was relatively straightforward.
Only a tiny percentage of the estimated three million Syrians who have sought refuge in Turkey have the necessary work permits. To survive they have to work illegally, without any rights, and for low wages. Providing a made-to-measure work force for the garment industry and a reminder that one person's plight is often another's opportunity.
I was able to see, first hand, how this exploitation works. It was just before 8am and a group of people had gathered on a street corner on the outskirts of Istanbul.
Picture: BBC/ Panorama
We filmed through the blacked out windows of our van a dozen yards away as the middleman picked this day's workforce, selecting them one by one. Those who were chosen boarded a bus to take them to a factory.
At least six of the workers on board were Syrian refugees. One was just fifteen and another, we'll call him Omar, was our source. We followed the bus until it stopped outside of a factory in an industrial zone a few miles away. This factory was known to us. We'd been told it made clothes for some of the world's leading brands.
I met with Omar later that evening and he showed me the labels from the clothes he'd been working on that day. I recognised them instantly and so would you. The brand could hardly be better known in the UK.
Over the next few weeks I got to know Omar and his friends. Like almost all of the Syrians I spoke to, they knew they were being exploited, but also knew there was very little they could do about it.
Some of them were being paid just over £1 an hour, well beneath the Turkish minimum wage. The fifteen year old boy told me that he wanted to be in school but he couldn't afford to not work. So he spends more than 12 hours a day ironing clothes that are then shipped to the UK.
All of the brands I contacted about this programme say they regularly inspect the factories making their clothes to guarantee standards. And some of these audits are unannounced.
But the Syrian boys explained how the factories got around this problem: when the auditors arrive, they are hidden out of sight. And when the auditors leave, they go back to work. It's as simple as that. Some of the brands acknowledge the failings in the auditing process and are now trying to tie up with trade unions and NGOs to combat abuses.
Other factories may never be visited by auditors because, as far as the brands are concerned, they don't exist. These factories are part of a chain of subcontractors who make up much of the garment industry in Turkey. They take orders from the so-called 'first tier factories' who are official suppliers to the brands, often without the knowledge of the brands themselves.
These factories are where you'll find the worst abuses of Syrian refugees and children. We followed delivery vans from one of the first tier factories, hoping they would lead us down their supply chain.
Our plan was successful but also darkly disappointing. We filmed outside one of the subcontractors as a small boy carried and dragged bags of material as big as himself to one of the vans. He couldn't have been more than 12.
We went inside, posing as the owners of a new fashion business. In the manager's office we immediately spotted a jacket that had been made for a British clothing retailer. It was quickly whisked away. Later, after browbeating the owners to let us see the factory floor, we saw the young boy again. He was carefully folding clothes at an ironing station. This boy was not alone - there were half a dozen Syrian children of a similar age in the workshop.
The United Nations say that there are more than 700,000 school-age Syrian children in Turkey. Efforts are being made to get them into education but it's estimated that as many as four hundred thousand are working, and many of them are working in the garment industry.
I spoke to some of the parents of these children. They don't want their kids working, but they say they simply don't have a choice.
One boy, aged just 13, told me he was between jobs. When we spoke he had just spent the entire morning looking for work but had no luck. I asked him what he would do now and he cried as he told me that if he didn't work, he couldn't live.
The evidence we have uncovered confirms that big fashion brands are profiting from refugees and their children. All of the brands involved say they are completely opposed to child labour and any exploitation of Syrian refugees, but our investigation shows that sometimes they don't know how, or where, their clothes are being made. Until the brands know exactly who is making their clothes, this type of exploitation is almost certain to continue.
Panorama - Undercover: The Refugees Who Make Our Clothes, Monday 24th October, 8.30pm on BBC One.Suggest a correction