The counter-demonstration that evening was violent and bloody, with both sides hurling stones at each other, and the Muslim Brotherhood claiming that several of its members were shot dead.

But also disturbing was the role earlier of what appeared to be a Muslim Brotherhood militia who seized protesters off the streets and took them for their own “interrogation” before handing them over to police.

“After they caught me they dragged me away and started threatening me,” said Walid al-Ganzouri, no youthful stone-thrower but a 35-year-old, British educated engineer. “They said they were going to kill me, and started beating me up.”

Along with scores of others, he was eventually handed over, bruised and with cuts to his head, to the prosecution service, which released them for lack of evidence. This did not stop Mr Morsi, during a late-night address, saying that “evidence from confessions” obtained from some of those seized showed they were plotting against the government.