My colleagues - and friends - in Brazil spent two months placing GPS trackers on illegal loggers in the Amazon. It's dangerous - but it helps us expose their crimes to the world.
Greenpeace activists in Brazil spent monitoring loggers near Santarém, the centre of the logging industry in the Amazon. Timber from sawmills there is exported all over the world.
Illegal logging can be hard to get to tackle. Logging happens deep in the forest, far from the eyes of the world.
But all that is changing. Covert GPS tracking technology and satellite surveillance means we can find out what loggers are really up to - and tell the world about it.
Read our report on the illegal logging trade in the Amazon.
During the day, logging trucks drove deep into the public forest - land owned by the government, where no permission to log has been granted.
We photographed them parked up in clearings, surrounded by logs.
As darkness fell, the trucks drove back to sawmills in Santarém.
They only carry timber on the public highways at night to evade the police. On one dead-end road - the PA-370 highway - we counted an average of 80 trucks loaded with logs each night. They were all bound for Santarém.
Now there may be a reasonable explanation for why loggers are shuttling back and forth between illegal logging camps and sawmills - and doing so at night.
So we checked government records to see where these sawmills claimed the timber came from. Then we used satellite analysis to check those estates and find out how much logging was taking place. We didn't find very much.
In fact, at three of the five sites, we found no evidence of logging at all.
This is a common trick sawmills use to launder illegal timber. They create a fake logging estate to get paperwork that persuades buyers overseas that their logs are legal. It's a well known scan - we even documented it in a report earlier this year.
Although this story starts in Brazil, it often finishes up over here. Companies in Europe are buying timber from these sawmills. Yet European laws ban the trade in illegal timber.
As technology gets better, cheaper and smaller, it becomes easier for us to turn the tables on illegal loggers and expose their crimes to the world. It also makes it easier for us to expose their customers.
Companies trading in timber from the Amazon are taking a massive risk. Until the Brazilian government brings the logging sector in the Amazon under control, timber buyers have two options. Either they take responsibility for the wood they're buying, making sure it's been harvested legally and sustainably, or they stop buying from high-risk regions like the Amazon.