NINETY thousand people attended this month’s Download festival at Donington Park but few will realise that they were unwittingly taking part in the biggest mass surveillance exercise undertaken by the police.

They had their faces scanned by strategically placed cameras installed by the organisers, who were able to compare their faces with those in a database of images of people who have been in custody across Europe.

Leicestershire Police has admitted that this big brother system has been trialled since April 2014 in “controlled environments” but obtained permission to use Download as the first major experiment at an outdoor event.

The police claim that the technology will enable them to find organised criminals who steal from festival-goers. But such active surveillance raises serious questions about the steady march of state surveillance of citizens over the past 15 years, as technology becomes ever more sophisticated and the supposed threat of terrorist attack increases.

More recently, Downing Street and the Home Office were challenged to answer allegations by anonymous government sources that Russia and China had broken into the secret cache of Edward Snowden files and that British agents had to be withdrawn from operations as a consequence.

Anonymous government officials were first quoted in the Sunday Times and then by the BBC, claiming that agents had to be moved because Moscow had retrieved information on how they operate.

The database used by Leicestershire Police is a lawfully held database of European custody photos drawn together by police forces across Europe and co-ordinated by Europol. Europol has its headquarters in The Hague, the Netherlands, and works closely with law-enforcement agencies in the 28 EU member states and with other non-EU partner states and organisations. It has more than 900 staff, around 100 criminal analysts and initiates over 18,000 cross–border investigations each year.

It is a massive part of the European secret intelligence network. Encouraged by terror laws, the authorities are increasingly using surveillance techniques in trivial circumstances — threatening civil liberties and pushing Britain further along the road to a police state.

The abuse of the Regulation of Investigatory Powers Act 2000 is by far the most serious part of the revelation last August that authorities made 500,000 requests to access phone and email records in 2008 — the equivalent of one in 78 adults coming under some form of state surveillance.

In last year’s annual report, surveillance commissioner Christopher Rose raised concerns about direct surveillance such as the bugging of public places, taking photographs of suspects and the use of covert human intelligence such as informants and undercover agents. Such techniques have long been part of police investigations into serious crime, but it is frightening to see these tactics routinely used.

Privacy campaigners have questioned the timing of the allegations against the Snowden documents, coming days after David Anderson issued his report on terror legislation which was commissioned by David Cameron.

Anderson criticised the existing oversight of the surveillance agencies and recommendations several changes. A new surveillance Bill, scheduled for the autumn, is expected to be the subject of fierce debate. Anderson’s report calls for a total overhaul of laws governing Britain’s intelligence agencies.

Snowden, a former National Security Administration contractor, handed over tens of thousands of leaked documents to the Guardian in Hong Kong two years ago. He left Hong Kong with flights booked to Latin America but was stopped in Russia when the US revoked his passport and has been living in Moscow in exile since.

Liberty director Shami Chakrabarti said: “David Anderson’s thoughtful report called for urgent reform of snooping laws.

That would not have been possible without Snowden’s revelations. Days later, an ‘unnamed Home Office source’ is accusing him of having blood on his hands. The timing of this exclusive story from the securocrats seems extremely convenient.”

Since the initial revelations about the extent of the bulk collection of communications data and the relationship between the intelligence agencies and internet companies, the US and British governments — and their intelligence agencies — have made a series of assertions that have subsequently been retracted. Snowden was initially said to be a Chinese or Russian spy, but the US has since said this is not true. The US has also backtracked on claims that surveillance helped stop 56 plots and that Snowden had “blood on his hands.”

The British government and intelligence agencies in both countries claimed that the Snowden disclosures had helped terrorists, costing GCHQ, Britain’s electronic surveillance agency, up to 30 per cent of its capabilities and that agents had to be moved. But no evidence had ever been provided to back up these assertions and Snowden has done a great public service by revealing the extent of illegal mass surveillance.