LONDON — In March, when British detectives began their investigation into the poisoning of Sergei V. Skripal, the former Russian spy, they had little to work with but mounds of CCTV footage. Heads bent over their desktop computers, they began the unglamorous work of poring through it, looking for an assassin.

Britain is one of the most heavily surveilled nations on earth, with an estimated one surveillance camera per 11 citizens. It has cutting-edge technology for visually identifying criminals, and software so sensitive it can scan an airport for a tattoo or a pinkie ring. And then there is that team of genetically gifted humans known as “super-recognizers.”

On Wednesday, the authorities announced that the effort had paid off: Two Russian intelligence officers had been charged with attempted murder, the first criminal charges in a case that has driven a deep wedge between Russia and the West.

Investigators released a cache of evidence, including security camera images that captured the progress of the two men from an Aeroflot flight to the scene of the crime, and from there back to Moscow. They also released photographs of the delicate perfume bottle that was used to carry a weapons-grade nerve agent, known as Novichok, to the quiet English city of Salisbury where the attack took place.