Supreme Court by Diamond Geezer/Flickr

The Supreme Court has confirmed that where the state retains data on individuals without their consent, it is interfering with their privacy even when that data is public.

But despite this finding the court ruled that the Metropolitan Police acted lawfully by keeping details of the activities of a 90-year-old pensioner with no criminal record as the interference with his private life was “minor”.

The pensioner John Catt launched legal action four years ago after discovering that police had secretly logged both his habit of drawing sketches of demonstrations he had attended and descriptions of his appearance and clothing. He wanted to force the Met to destroy this data.

Last year the Court of Appeal found in favour of Catt. It said the police had not demonstrated how the data on Catt could help crime-fighting and that such storage of personal data involved “a significant interference” with privacy rights.

Reversing that decision today, the Supreme Court said it was satisfied that the Met’s data-handling regime, under which information was “regularly reviewed for deletion” meant there was no significant interference.

The Supreme Court then went on to say the amount of labour required to delete information relating to persons such as Mr Catt from the database would be disproportionate.

Catt is now applying for permission to take the case to the European Court of Human Rights.

In a press statement released by his lawyers, he said: “I cannot agree that the police in this country should be trusted with information about innocent people’s lawful political activities. In my view, without a new system of rules governing police surveillance, there is too much scope for the police to abuse their powers.”

Campaign group Netpol, which intervened in the Supreme Court hearing by providing evidence, has described the Supreme Court’s ruling as “judicial approval for the mass surveillance of UK protest”.

However the Court’s confirmation that collection of data on a searchable database interferes with personal privacy may be helpful to other cases challenging the GCHQ’s bulk collection of communications data from internet cable taps.

Barrister Conor McCarthy said: “The Court was unanimous in finding that the systematic retention of personal information by the police in itself interferes with an individual’s right to private life under Article 8 of the European Convention on Human Rights and therefore required justification. The judgement illustrates that any such justification will be carefully scrutinised by the courts.”

He added: “The Court’s confirmation that the mere retention of data falls within Article 8 and requires justification if it is to be lawful has potentially important ramifications for other cases, especially those relating to the mass interception, collation and retention of communications data.”

The Bureau of Investigative Journalism is challenging GCHQ’s cable-tapping programme, known as Tempora, in the European Court of Human Rights, on the grounds that it breaches privacy rights and also limits journalists’ ability to protect their sources.

The government must respond to the Bureau’s case by May 6. It will need to convince the European court that the privacy interference caused by the bulk data collection is proportionate and justified.

Sir David Omand, a former head of GCHQ, has previously compared the agency’s searches of bulk data to automated audit systems used by banks to search for potentially fraudulent transactions.

Speaking at a debate on the London School of Economics in January 2015 he said: “Do I worry that the bank’s computers are looking at my most intimate details? No I don’t, I get a benefit, the bank gets a benefit.

“Do I worry that GCHQ’s computers are whizzing through my data looking for somebody else’s data that they have a reason to suspect they ought to look at? No I don’t. There’s almost a philosophical question we need to address there.”

Related story: Bureau files ECHR case challenging UK government over surveillance of journalists’ communications