A war of attrition. A war of trial and error where the front-line soldiers drink coffee, eat junk food and wear jumpers in windowless rooms. A war of hacking, of firewalls, of fingers blurring over keyboards using every method and technique known and inventing more as they go along.

Berlin is a thriving metropolis of over ten million inhabitants, but where there are people, there is crime.

Nearly every business has CCTV. High-quality, real-time, full-colour footage that has to be retained for thirty days to comply with insurance policies. Such large data volumes mean that the only viable storage method for most businesses is cloud storage. A virtual bank where the footage can be uploaded and held for the required time in exchange for a monthly fee. The cloud storage operators promised state-of-the-art security and impenetrable systems.

The soldiers aim their weapons at those systems. They hack and find engineer access points. They delve, look, seek, search and slip out as unseen as their entry.

The private hospital does not have CCTV, but they know a van delivered the men. Where did the van come from? They have the end destination so they work backwards. Hacking businesses to view footage to see angles of roads and junctions in the hope of catching a glimpse of the van.

It works too. They establish the make and model of the vehicle. They establish the colour. They write code and algorithms to embed in hacked systems to do the work for them at a processing speed far higher than the limitations of the human brain permit. They scour, dismiss, negate and pass over thousands of hours of footage from tens of thousands of cameras.

They quickly establish that the van took a very circuitous route and appears to have travelled random roads in an impulsive manner. That suggests a very basic awareness of surveillance. They know this, as an advanced state of surveillance awareness would mean the van never appearing on any footage anywhere. Which would be hard but not impossible. There are crime prevention and detection websites that show maps of the known fixed points of cameras within predefined areas. Simply open the map and pick a route that goes past the least number of cameras. The van has not done that. Instead, it has simply driven round Berlin for a while before heading to the hospital.

The method is not perfect, but it helps.

A grey, brick-built warehouse on a back road in central Berlin.

The van is tracked to the very centre of Berlin. To the old part of the city. Architectural historians are consulted.

Not all brickworks made grey bricks. Some made red bricks, and those red bricks generally ended up in certain areas. Others had a yellow colour. They ended up in other certain areas. History shows us these few brickworks made grey bricks, which served these geographical sections of the city.