In Rabbi Jonathan Romain's conversion class, there have been couples converting together, religious Christians, an ex-Muslim convert, policemen, soldiers and housewives.

But although converts come to him from all walks of life, as the Movement for Reform Judaism's conversion expert Rabbi Romain has identified some key trends.

Around 90 per cent come with a Jewish partner; there are around five times as many women as men and a disproportionate number of Catholics. Most common of all is the reason converts give for being attracted to Judaism. It's the sense of family, culture and "camaraderie", said Rabbi Romain.

"There's always an accusation that they are just doing it for the sake of a white wedding, but 50 per cent of converts are already married. They like the faith, the family, the tradition and way of life. We like it, why should we be surprised others like it?

"It is not a bad thing that many convert with a Jewish partner, Judaism is a family-based religion, and if you have a Jewish partner you are rooted into it. Although there are people who come alone, it is much harder for them. It's hard to do Pesach or Shabbat for one, to be Jewish on your own.

"But most people who marry a Jew don't convert, it's not easy, it's extremely difficult in the Orthodox, and takes at least a year in the Reform. You are taking on a heck of a lot. No-one would really do that just for a 20 minute
ceremony."

Intermarriage would appear to be an increasing trend, with Rabbi Romain's annual "I'm Jewish, My Partner Isn't" seminar recording double the number of couples attending last month.

But conversion rates over the last five years have stayed remarkably steady, apart from Liberal conversions. Eighty-five people converted through the Liberal movement last year, up from 71 the previous year.

In the Reform Movement, 106 adults and 39 under-16s converted in 2011 and this figure has been steady for the last 25 years, with no significant rise or fall in numbers. Conversions do take place in smaller communities, as long as a rabbi can supervise, and last year seven people converted in Glasgow and 11 in Manchester.

Rabbi Romain said steady figures could indicate "rabbis may not be proactive enough in reaching out to mixed-faith couples. Most will see the conversion process as utterly impossible, intimidating. Yes, of course, it involves effort and commitment, but it is for ordinary people."

Orthodox conversions are also steady at around 35 people a year, apart from a bumper crop of 54 in 2009, under the auspices of the London Beth Din.

The process, which includes a period of around six months living with an observant Jewish family, takes between three and four years, sometimes longer. Prospective converts with a Jewish partner take up around half of the Orthodox intake.

Daniel Greenberg has tutored Orthodox converts for the London Beth Din for a decade, and is the author of How to Become Jewish (And Why Not To). He feels strongly about the discrimination still faced by converts. "We have a racist attitude to converts. I was once with a group of Orthodox Jews, one of whom made a disparaging comment about converts, which I rebutted. He said, 'Yes, but you wouldn't want one in your family.'

"I would love my children to marry someone as turned-on religiously, and as inspiring, as real converts. These people often see more in it than we do. It is something to be proud of."

Rabbi Romain agreed. "Other faiths are much more welcoming, they see it as a compliment, and we see it as a threat. I don't know why we are so nervous of other people."

Zahavit Shalev, who runs an 18-month Masorti conversion course at New North London Synagogue in Finchley, said it was often single female Masorti converts who were most worried about potential discrimination.

"They are worried they will not find a partner in this Jewish world. It's a litmus test for a potential relationship, if it's a problem. And they know there are potentially problems for their children in the Orthodox world, or they could fall in love with someone who objects to their status, which could be horrible. We talk about that in the classes."

In the Masorti movement, Ms Shalev said, they were normally accepting of conversions made via Progressive batei din. "We would very likely accept someone who had had a Liberal conversion, if they went to mikveh and a beit din had approved their conversion. But no circumcision would be an issue for us."

Mr Greenberg was adamant that only someone with true dedication to Orthodox Judaism should attempt to convert via the London Beth Din. "I advise people that if they are at all interested in Progressive Judaism, convert through the Reform or consider not converting at all. If you are considering intermarriage, and the only reason to consider converting is to avoid a row, then just be a man, have some guts and intermarry. You have not been given a good enough reason by your parents, intellectually or religiously, why you should not.

"This is unusual advice," he admitted. "People do take the line that if we do not lower the bar, the community will shrink. I say, we'll still daven while we've got a minyan. The religion is something I believe in very strongly, and if someone wants to join me in it, they are very welcome. But they can't do it for the piece of paper."

Converts are not often grilled about a belief in God, which can be hard for converts from non-religious backgrounds to express. Mr Greenberg said: "The conversion process run by the London Beth Din is about religious practice. But I did have a candidate who told Dayan Binstock he would do everything but he did not believe in God, and did that matter? Of course, the dayan said, 'Sorry, it does, you're out.'"

Ms Shalev from New North London said it was tricky to navigate. "We can't read your mind, that's between you and God. All we can do is pass judgment on how well you are leading a Jewish life."

Rabbi Romain takes a different approach. "My view is that you don't have to believe in God, you just have to do what He says. There are many different ways of being Jewish, and as long as the culture, values and tradition are real for you then it does not matter if you have questions over the theology."

Hardest for converts can be the acceptance of their own families. Mr Greenberg said that there was a responsibility to acknowledge a convert's roots, and no rabbi should demand that they broke with their family. They may visit at Christmas and even sit shivah for non-Jewish parents.

"Halachah can adapt to human sensitivity far better than people think. Even saying kaddish is not a problem halachically. And emotionally it's very, very important. They should recognise where they come from. I cannot think of any of the converts I have taught, of whom I am most proud, who have broken from their families as part of the process."

Rabbi Romain agreed: "Honour your mother and father still applies."