In the 12 months since Edward Snowden delivered his first revelations about state surveillance in the US and Britain, there has been a fierce debate over co-operation between the security services and the communications industry.

The intelligence agencies in the US and UK have argued that they must retain access to the public’s phone and internet communications if they are to counter the threat from those who espouse terrorism and plot violent acts. Civil libertarians have replied that the security services now have access to so much data that they can snoop effortlessly on the innocent.

This debate has been brought to a head in Britain by a ruling from the European Court of Justice in April. The court struck down regulations under which telecommunications companies and internet service providers were required to retain data for up to 12 months and supply it to security services on production of warrant. As a result – and much to the alarm of the UK’s security chiefs – the communications groups have been preparing to destroy many files.