William Carter, prosecuting, told a jury at Cambridge crown court on Monday that Bukovsky’s computer was identified during an operation by the Child Exploitation and Online Protection Centre. Police arrested him in October 2014 at his home on the outskirts of Cambridge.

Bukovsky, who was expelled from the Soviet Union in 1976, told detectives he had indecent material, the court heard. “He [Bukovsky] responded immediately by saying he did download images and that they would be on the computer in his study,” Carter said.

The police subsequently discovered “a very great deal of material” on two hard drives. It showed some “very young” children up to the ages of 12 and 13. They were “largely but by no means exclusively boys”, the court was told. There were some adults involved.

In an interview, Bukovsky told detectives he had become interested in child abuse images in the 1990s in the context of a debate on the control and censorship of the internet. “He became curious,” Carter said. Bukovsky then looked for and discovered this material online, the prosecutor said.

“Bukovsky said his initial curiosity turned into a hobby, rather like stamp collecting,” Carter said. The dissident continued to download images between 1999 and 2014, and estimated that he had accumulated a collection of “1,500 movies”. His interest varied year by year. The last downloads took place days before his arrest.

“His computer was looking for material constantly,” Carter told the jury. “Mr Bukovsky said in essence he didn’t see what harm he was doing. He said the children in most of the material looked as if they were enjoying themselves.”