The last time I heard from my friend John Marsden was exactly a week ago, when he emailed to congratulate me about something. A writer of his calibre, a principal of two schools – yet he always took the time to write. Not just cursory one-sentence emails, but wonderful, philosophical musings about parenting, politics, about the powerful and the powerless.

When I was first published in my 20s, and quite overwhelmed by writers’ festival events, John was the steadying, kind presence that grounded me. He didn’t give a crap about prestige, he had no respect for unearned authority, and when he gave a speech he always addressed the students or young people in the room instead of the eminent adults. John was an introvert – sometimes could barely look another adult in the eye – but when he spoke to young people it was truly transformative: he wiped the boredom from their faces. They sat straighter, they lit up, they laughed. He truly got them.

Decades ago, John – who worked full-time as a teacher for much of his career – took his students to an abattoir when they told him they were bored of their text Bless the Beasts and Children. You can’t do that these days but this was the sort of teacher John was. He believed young people should fully engage with their world, and he understood that they had more courage than adults were generally prepared to concede.

As a teenager at school, my mates and I passed around his bestselling Tomorrow, When The War Began series, even though some teachers were trying their best to get them banned. For us the war wasn’t in a fictional tomorrow, it was in our immediate pasts. Our parents survived Cambodia, Bosnia, Vietnam. Some of our friends were unaccompanied minors who’d survived rickety fishing vessels and pirate attacks. We understood how the line between childhood innocence and adulthood responsibility was often determined by luck and privilege, and so did John.

John’s youth was harrowing in different ways, and he never hid the fact that he was a bit bruised by life. He became suicidal as a university student and was institutionalised; he once wrote that the world of the psychiatric hospital was in some ways “more real than the one outside. In here the masks are off, people don’t pretend so much. [They] don’t have the energy or strength.” Perhaps that’s why he was able to inhabit his characters so fully. It is extraordinary for a man of his generation to write teenage girls so convincingly and with such empathy.

John was the sort of rare person born with what Ernest Hemingway calls a “built-in bullshit detector”. He once said, “I consider it a disturbing aspect of our culture that most young people can become adults merely by staying alive and having birthdays.” John’s life’s work was about specific actions rather than sweeping, grandiose ideas. When I taught a residency at the Alice Miller School he founded, I saw this in action. John said that “we kill all the caterpillars, and then complain there are no butterflies”. He wanted young people to thrive – to allow themselves to feel and understand the full spectrum of emotions, not just the pleasant ones but the unpleasant ones as well, like envy, rage, despair and grief.

John Marsden was a literary and educational giant, but as a friend and mentor he was someone very special – someone who instinctively understood the most vulnerable-feeling person in a room, including a first-time Chinese-Cambodian author who could present onstage but couldn’t look any individual adult in the eye because she’d been taught that this was culturally rude. John taught me, by example, that shyness was not a barrier to getting things done or to having strong convictions.

Every time I wrote a book he read it and cheered me on. I still can’t believe I will never see him again. But always philosophical about life, he once wrote to tell me:

I was trying to figure out this morning, in a vague existential sort of way, why we attach so much importance to our lives when, without a religious belief, it’s hard to know why they have any value or purpose of meaning. Needless to say, I couldn’t come up with any answers :-)

John’s smiley face emoticon conclusion said everything – about his inquiring mind, his ability to hold doubt central to his life, and yet still feel cheerful hope despite not finding definite answers. His joy was a hard-won one, and his love and concern for others was expansive.

I will never forget my friend John Marsden. He was not just admired, but so loved by all those whose lives he changed.