John Catt was born in January 1925 and has been a peaceful activist since 1948, regularly attending public demonstrations.
He became involved with campaign group Smash EDO – which aimed to shut down the US-owned company’s weapons factory in Brighton.
Mr Catt was twice arrested at demonstrations for obstructing a public highway but never convicted of any offence, the European Court of Human Rights (ECHR) ruling said.
In March 2010 he made a subject access request to the police under section 7 of the Data Protection Act 1998 to find what information was being held about him.
He discovered 66 entries which mentioned him between March 2005 and October 2009 held on an “extremism database”.
He asked the Association of Chief Police Officers (ACPO) to delete the entries but this was refused and no reasons were given.
They recorded his attendance at Smash EDO demonstrations, attending a Trades Union Congress conference in Brighton in 2006, a Labour conference in Bournemouth in 2007, a pro-Gaza demonstration in Brighton in 2009 and at a demonstration against “New Labour” organised by a number of trade unions later that year 2009.
Police recorded his name, date of birth, address and presence at the events. Descriptions of him were noted and a picture of him stored.
In January 2012 the HM Inspectorate of Constabulary published a report on undercover police operations designed to obtain intelligence about protest movements.
The report concluded Catt’s information was being unnecessarily retained in police records.
After this, the number of records mentioning Mr Catt was “apparently” reduced to two but during later court proceedings the Government revealed it had found a further four records still held on him, the ruling said.
In 2015, in response to a second subject access request, police told Mr Catt the records were held to “help UK policing manage a future risk of crime – of which [you] could be the victim. The records themselves should not and will not be disclosed [to you] for what are obvious reasons.
“An intelligence database loses all efficacy if it is not kept confidential.”
The ECHR judgment said: “The Government stated that the police could not provide any explanation of why the reports were not disclosed previously. However, they were investigating the matter.”
Recording its findings after deliberations held in private, president of the chamber Linos-Alexandre Sicilianos, sitting with some six judges and a registrar, said in the ruling: “The applicant, who had never been charged with any crime, nor accused of any violence, nor suspected of being directly involved in criminal activities undertaken by the group Smash EDO, and who had been assessed as not being a threat ended up having personal data relating to his participation in demonstrations and trade union events, and thus to his peaceful exercise of the rights protected under Articles 10-11 of the Convention, kept on police records in a searchable database for an indefinite period.
“Even the existence of the database in question was not clearly acknowledged until the domestic proceedings in this case.
“A subsequent review of matters relating to undercover police operations, prompted by allegations made by whistleblowers, also led to a review of the database on overtly obtained intelligence, resulting in the deletion of part of the data originally retained concerning the applicant.
“As pointed out by the applicant in his submissions, a system that must rely on whistleblowers, litigation and press disclosure to ensure proper conduct is not adequate in terms of protections against abuse or arbitrariness.”