One of the most touching beliefs of evangelical Christians is that they actually convert people. It isn’t entirely false – but it’s hardly ever true.

Nonetheless, under Justin Welby, the Church of England is showing worrying signs of believing its own propaganda, with a report on some recent polling that shows that most people dislike being talked to about Jesus, and are less inclined to believe in him if they are talked to on the subject.

You might think that this would be discouraging, but to the report’s authors the moral is absolutely clear: “So we need to talk about [Jesus]: to more people, more often, and more relevantly.” Along with 85% of the respondents they consider “practising” or real Christians, they believe it is “important or very important” to talk to non-Christians about Jesus.

Many are convinced they are already doing this. A third report talking about Jesus to non-Christians every week. This is literally incredible. If true, it would mean that every single non-Christian in the country gets talked to about Jesus every six months. But when asked, non-Christians reveal that they are entirely unaware of all this evangelism. Nearly half have never had a conversation about Jesus. A third don’t think they know any Christians at all, let alone evangelicals.

This may be, of course, because Christians appear alarmingly normal. Among the Christians actually known to non-Christians, very small proportions are described as narrow-minded, hypocritical or homophobic, even among younger people. This contrasts quite clearly with perceptions of Christianity or of the institutional churches revealed by other polls. But I’d guess that a part of this normality is that they don’t in fact talk much about Jesus, however much they may believe or hope that they do.

Two recent books suggest why this happens: Anna Strhan’s Aliens and Strangers, a study of a prosperous hardline evangelical church in London, and Det Gudlösa Folket (The Godless People), a study of Swedish secularism by David Thurfjell. Both touch on the question of why Christianity has become embarrassing. This turns out to have a precise and illuminating answer: because embarrassment is one of the emotions that seem common to all human cultures and to display in the same ways, so that people can accurately identify an embarrassed expression or posture on a stranger.

It is exhibited by a kind of painful cringing gesture, which is provoked when the subject becomes conscious that they have violated the norms of their own group. When I am in England I am not in the least embarrassed if I walk around the house with my shoes on, but when I catch myself doing it in a Swedish house I squirm, because there I learned to take them off at the door.

The problem for the Church of England, and to some extent for the Church of Sweden too, is that white middle class people are no longer expected to be Christian. So when they reveal that they are, it can be an occasion for embarrassment all round. The Oxbridge and public school Christians in Anna Strhan’s study did not have any difficulty proselytising if they were doing volunteer social work on council estates at the weekends. Then they were outside the constraints of their class. But in the hedge funds and City law firms where they worked, they could not talk about their faith. It was just too embarrassing, not something people do.

Similarly, it was members of the moderate and mainstream acceptable Church of Sweden who found their religion embarrassing; pentecostalists and other social outsiders were happy to talk about faith.

Once you have defined yourself as an outsider, and Christianity as part of that outsiderishness, then it becomes quite easy to talk about your enthusiasms. The trouble then is that very few people want to join you in the outside group.

The most reliable way to become an evangelical Christian, the survey found, is to be born into a family of them. Only 7% of the evangelicals surveyed had been converted in the past 11 years. No wonder they think they have to talk more loudly and more often, and screw up their eyes tight shut against the evidence.