Hakham Meir Rekhavi, who is acknowledged as the Diaspora leader of the Karaites, only found the time to devote himself to his chosen cause when he had to become a full-time carer for his severely disabled daughter Hanna.

He was born Martin Furman into a traditional Leeds Jewish family and was a pupil at Leeds' Allerton Grange School and later Roundhay School

Meir's mum Fay, who still lives in Leeds, was not satisfied with the educational standard at the local Talmud Torah, so she sent him to the more religious Shomrei Hadass cheder.

But not seeing consistent Jewish practice at home, Meyer's cheder education made little impression on him.

However, as a teenager Meir, who did not perform well at school due to his undiagnosed dyslexia, began to think about what Judaism meant to him.

He recalled: "At the age of 15, I did not see a point in sitting on the fence. You were either in or out of Judaism. But I decided that I needed to know what I was opting out from, otherwise I would be an ignoramus."

Battling against his dyslexia, Meir began to read up on Jewish history and noticed a constant theme of Jewish martyrdom in the Maccabean, Roman and medieval periods.

He realised that there must be something to Judaism if people were willing to die for it.

He said: "That had a lasting impact on me."

With this realisation, Meir became more religiously observant and began to attend Bnei Akiva.

But he said: "I was caught between two worlds. I did not come from the same background as the BA kids, whose parents saw me as rebel not to be mixed with.

"And I was still into contemporary music and going to nightclubs, where my non-observant friends began to look at me as though I was weird because I was becoming religious."

Leaving school after O-levels, Meir made aliya at the age of 17 to study at Jerusalem's Ohr Samayach Yeshiva.

But he found the yeshiva "intellectually and emotionally stifling", especially when students were urged to take Midrashim about the mythical gigantic height of biblical figures literally.

That was when Meir began to question rabbinic Judaism, which he considered, had been affected by Zoroastrian and Gnostic influences. So he moved to the "more open" environment of Midrash Sephardi in the Old City.

But even this failed to satisfy him until he walked into the nearby Karaite synagogue where he found the fulfilment of his dreams and the answer to all his baffling questions on rabbinic Judaism.

He said: "It seemed to me a purer form of Judaism, based on the original T'nach rather than on alien, non-Jewish influences."

Not surprisingly, Meir - whose Karaite views and rejection of the oral law were considered heresy - was asked to leave his Sephardi yeshiva.

He took refuge in the small Karaite community where he was taken under the wing of their leader Hakham Mordecai Alfandari, whose mantle Meir took on the hakham's death in 1999.

Meir's intensive studies with Alfandari were of an informal nature.

He said: "He was like my spiritual father. He had a way of teaching, which has been lost.

"I was privileged to go on long walks with him, during which we had discourses without texts, because he knew the T'nach by heart.

"He also knew seven or eight languages, as well as agricultural knowledge, mathematics and science to help with the practical application of Torah."

Meir explained that although Karaites did not accept rabbinic halacha, they had their own halacha in order to apply Karaite law to modern circumstances.

For instance, Meir said that his son Dvir, who is currently studying bio-medicine at Manchester University, recently asked him the Karaite view on stemcell research.

Meir himself applies Karaite law in his own Edgware home fairly leniently by allowing the use of electricity on Shabbat, although the Torah forbids the use of fire in one's home. But he draws the line at central heating and the use of a slow cooker or hotplate to keep food warm.

He said: "The Torah is not about convenience, but about truth.

"The law is very specific about not letting a fire burn in one's habitation on Shabbat.

"To me Shabbat is not about eating, but about praying, sleeping, Torah study, reading and playing with one's kids. We eat cold things on Shabbat."

But the transition to a Karaite way of life was not initially easy.

Meir recalled: "I had a lot of baggage to cast. Karaites do not wear tephillin, as they consider the command allegorical.

"But it felt weird not to wear them, as I had been brainwashed from the age of 12."

In between all this religious mentoring, Meir's life continued, initially with a couple of months' ulpan on a West Bank settlement, which Meir regards as "not a settlement but a part of Israel".

He then rented a Jerusalem apartment, trying desperately to make ends meet by working double shifts in a pizza restaurant in the days of hyper-inflation.

He was then drafted into the army, serving as a combat engineer in an elite unit working secretly with explosives.

On his demob, to get his difficult army experience out of his system, Meir returned to Leeds, where he joined his brother Eric in the family fashion business.

Eighteen months later in 1989, he returned to Israel with a scholarship to study medicine at Beersheba University.

Meir explained: "In the army I had wanted to be a combat medic.

"But the powers-that-be had other ideas. Basically you've got it made if you're a combat paramedic. It is an open ticket for jobs.

"So I applied for Israeli universities, scoring high points in the psychometric examination which I took while still in England. But it became a fiasco.

"As I had not done A levels, I had to do a university preparation year in Beersheba.

"After I started the course, I was told that the scholarship was only for the preparation year. I did have a complete scholarship and wanted take the matter to court.

"But I was told by my lawyers that I would not win, even though I had evidence. With the influx of Russian doctors to Israel no one else was getting scholarships."

Moving back to Jerusalem after his aborted course, Meir decided to do plumbing, as he was told that plumbers earned more than doctors. But he discovered that although he wanted to build up the country, he was not a plumber.

In 1990 in a secret Karaite ceremony, Meir married his London-born wife Hazel Bensusan.

I asked Meir whether Hazel, who hailed from an assimilated Sephardi family, had also been a Karaite.

He replied: "She agreed to be one."

So was he missionary?

He replied: "All Karaites are by definition missionaries to bring people back to the Torah."

Yet Meir, who in 2005 set up the first-ever Karaite conversion course for non-Jews, has made no converts in the UK where he practises his beliefs in splendid isolation, praying at home alone with his family.

Meanwhile by 1993, after son Dvir was born, the family could no longer survive financially in Israel. So they returned to Leeds where Meir studied computer engineering at Leeds Metropolitan University.

Then in 1995, daughter Hanna was born severely disabled after a very premature birth.

Meir, who was blessed with the patience to cope with Hanna's major operations and later had to accompany her to Brodetsky Primary School where she was fully statemented, found himself her full-time carer.

He said: "It ended my career as a computer engineer. At first it was very difficult because I was in and out of work because of Hanna.

"Then I realised I could get benefits as a full-time carer."

He continued: "Every grey cloud has a silver lining. Being Hanna's carer gave me the time and patience for my personal development. I was able to devote my evenings to my Judaic studies and writing articles on Karaite issues."

The family, including younger daughter Oriyya, later moved to London to be nearer Great Ormond Street Children's Hospital which Hanna attended.

In 1999, Meir set up a Karaite website and in 2005 the online Karaite Jewish University which provides 18-month conversion courses for non-Jews, as well as educational courses for rabbinic Jews wishing to become Karaites.

Meir has become the Diaspora's supreme authority on Karaite conversions which take place in San Francisco.

He is regarded as the leading Karaite authority outside Israel.