People inside Iran have felt the effects of the restrictions. More than 5m websites are blocked in Iran, including Facebook and Twitter (but Google+ is still accessible). Millions of Iranians get round blocked addresses with help from proxy websites or virtual private network services, but in recent weeks users across Iran have complained about unprecedented difficulties in using VPN services.

“I have no idea what has happened but VPNs hardly work these days,” said Hassan, a Tehran citizen. “There are times when the internet is dead in Iran. A few weeks ago, on the very night when the regime announced the final list of candidates and the disqualifications, VPNs were completely down. It shows they feared revolt and were clamping down harshly.”

Iran’s constitutional body, the Guardian Council, has barred a large number of candidates from standing in the 14 June election. It allowed only eight candidates to run, and disqualified former president Akbar Hashemi Rafsanjani, the opposition’s favourite, from standing, to the dismay of the country’s many reformers.