“Oh yeah, I’m scared,” agrees Nasreen (not her real name) a feisty 29-year-old asset manager from east London who has been a semi-closeted apostate for nine years. “I’m not so worried about the loonies because it’s almost normal now to get threats. What worries me is that they go back to my parents and damage them, because that’s not unheard of.”

The danger is confirmed by Imtiaz Shams, an energetic 26-year-old who runs a group called Faith to Faithless, which aims to help Muslim nonbelievers speak out about their difficult situations. Shams has a visible presence on YouTube and has organised several events at universities. “I am at physical risk because I do videos,” says Shams. “I don’t like putting myself in the firing line, but I had to because no one else is willing to do it.”

As real as the potential for violence might be, it’s not what keeps many doubting British Muslims from leaving their religion. As Simon Cottee, author of a new book The Apostates: When Muslims Leave Islam, says: “In the western context, the biggest risk ex-Muslims face is not the baying mob, but the loneliness and isolation of ostracism from loved ones. It is stigma and rejection that causes so many ex-Muslims to conceal their apostasy.”