The sorry few who have seen inside his or her gilt-edged hideaway tend only to have done so after being summoned for disciplinary matters. For all others, its whereabouts remain a mystery.

This is why I am, perhaps, a little taken aback to find Charles Dormer’s headquarters nestled amid the busy classrooms of Immanuel College in Bushey, with no intermediary secretary to act as buffer.

What is more, during our chat, there is a casual knock on the door; two sixth-formers have excitedly come to tell their headteacher — who is also their English teacher — that one of their preferred texts just appeared on their mock exam. Metaphorically, his door is open.

But the head of the £16,500-a-year private school will be receiving pupil visits only for a few months more. Last Thursday, the governors and he surprised many parents and pupils with the announcement that he would be leaving next year after five years in the job.

“After a wonderful time,” he told them, “I have decided that it is my time to move on”.

Further details have not been forthcoming; but speaking to Mr Dormer, one is left in no doubt that his lifelong passion for teaching, and learning more along the way is constantly pushing him to expand his horizons.

“People often become teachers because they want other children to have what they did not have,” he says. “That is my case. I can’t replace the childhood I didn’t have, or the education I didn’t easily receive but I would like others to have the education I did not.

“One of my aims over the next 20 years or so is to have a more diverse contribution to education.” He hints that moving on to a state school could be on the cards.

Born in the United States, Mr Dormer, 49, spent his early childhood in Miami, where he attended a private school that, although heavily populated by Jewish children, offered no religious education. At home, he was raised by “strong, protective women who feared antisemitism and thought their duty was to keep me safe by downplaying our heritage”.

He came to the UK aged eight and lived in Leyton, east London, where “bullying, racism and antisemitism simply happened”. He remembers being chased with sharp objects down the street, and that his school in Woodford Green failed to erase a two-foot high graffiti message declaring “Clock End skins kill Tottenham yids” from its sports playground.

“Childhood in those days involved a great deal of fear of attack,” he says. “You lived in a permanently guarded state.

“You were constantly reminded you were a Jew and therefore greedy, avaricious, flat-footed, big-nosed. Foreigners, immigrants, international people stuck together because we all felt excluded together by that racism and xenophobia.”

This is one of a myriad reasons he feels particularly proud of having stood at the helm of a Jewish school; especially one, he adds, which contains “the most ethnically diverse group within the Jewish community that I have ever had the privilege of being in”, with families originating from across the Middle East and north Africa, as well as Europe.

He regrets his own lack of learning in the faith from a young age.

“You do become a teacher to fill in the gaps and to help other people make better choices than those that were available to you.

“I passionately believe you have to give a child what you believe is your best understanding of your heritage and right or wrong, and teach them to think for themselves — and then let them choose.

“We teach them how to be constructive parts of their community; then teach them how to relate with other communities and the rest of the world. To shine their light, they must first know what their light is.”

Fresh from Cambridge University in the late 1980s, Mr Dormer began his teaching career working at independent schools in south London, before taking over the headship of Sir Isaac Newton’s alma mater, the King’s School, a grammar school in Grantham.

Then, the Immanuel job cropped up, coinciding with his wish to return to north London to care for an elderly relative. He was astounded, and delighted, to discover that the options for Jewish education had multiplied since he was a child; by taking the headship, he almost righted a wrong of years of hiding his Jewish identity. He arrived at the college in April 2012.

“We offer an academic education infused with Jewish light, a pastoral education infused with Jewish light; and a Jewish and Hebrew education,” he says.

“What is more, all these three things need to be understood by a child as a British citizen, as a global citizen and also from the perspective of Israel.

“Jewish education says you cannot separate the heart and the mind, that they go together. What the run of British state education might benefit from discovering more of is the importance of the heart to the head, as well as the importance of the family to the child in the school.”

While he understands some people’s aversions to a private education, he counters: “I wouldn’t like to see a world where people who had honest money and paid their taxes were banned by law from spending their money to educate their children.

“If such schools are going to exist, it is good that one of them is a Jewish faith school that serves the Jewish population.”

Instead of competing with schools such as Yavneh and JFS, he says, Immanuel stands as a viable alternative to secular, private options in the area, such as Haberdasher’s, Highgate, UCS and South Hampstead High School.

In response to the suggestion that the creation of a new Jewish free school in north-west London could put pressure on Immanuel, he says “as long as Jewish education and the community as a whole is strengthened by additions to the team, bring them on”.

Immanuel currently enjoys its largest student roll to date — 650, including its preparatory school, which was opened five years ago. The college was placed 34th in the Daily Telegraph’s independent school league table, above rivals Merchant Taylor’s and Highgate.

Dormer remains committed to what he believes is the headteacher’s fundamental role. “Your aim as a head is to make yourself be bettered by students,” he says, “who don’t even necessarily look back because they have so much to see looking forward.”

“A great educator aims to make a pupil so strong that they don’t need that educator anymore. I am not claiming to be a great educator, but I am saying this is what I aspire to be.

“The more people who succeed and no longer need me, the better job I have done.”

It is, he explains, this sense of purpose — of no longer being needed — that has led to his resignation.

“Immanuel’s strong improvements on all fronts is exactly why I feel able to leave,” he says. “I love finding ways to help people, particularly through education, and Immanuel can make its own way forward now without me.”

He will miss most “some great colleagues, many great characters among the students and some parents who have actively made us a better school through their efforts”, adding he is “looking forward to what comes next”.

What that will be is still unclear but, having begun his MA in Jewish education at the London School of Jewish Studies in October, he feels he is finally filling in the gaps from his childhood.

“I believe we have the power in our lives to make ourselves more complete and I am completing a part of myself that was incomplete,” he says. “Or, really, it’s more about becoming. I am certainly now enjoying becoming something that I was not able to become before.”