Every corner of the Potterverse mourned the loss of Robbie Coltrane last October.

Before he left his sizable stamp on the cultural phenomenon that was the Harry Potter franchise, the Scottish actor had enjoyed a prolific career in film and television, and was made an Officer of the Most Excellent Order of the British Empire by Queen Elizabeth II for his services to drama. But it was his portrayal of lovable half-giant Hagrid, the Hogwarts gamekeeper who looks out for Harry and his mates, that secured his cinematic immortality—in both the hearts of the movies' fans and the young actors who basically grew up on set.

Tom Felton, who was 12 when he was cast as Potter nemesis Draco Malfoy, has his own stash of memories from those formative days when he and his fellow newcomers cut their acting teeth alongside a who's who of British cinema. And in honor of what would have been Coltrane's 73rd birthday March 30, the author of Beyond the Wand: The Magic & Mayhem of Growing Up a Wizard penned a tribute to his late co-star exclusively for E! News:

In the early days of Harry Potter, the cast comprised two distinct groups: children and adults. Emma Watson was 9 when we started shooting; Dan Radcliffe was 11; I was 13. Maggie Smith and Richard Harris, by comparison, were in their sixties and seventies. Do the math: You were either one of the kids, or you were one of the grown-ups.

Unless, that is, you were Robbie Coltrane.

Somehow, Robbie managed to be an adult and a child at the same time, maintaining a foot in both camps.

His knowledge of the world was astounding. He was well-versed in any topic you might care to mention, from engineering to geography, from history to travel—and that meant he had something to contribute to any grown-up conversation that might be happening on set. You could tell that the older actors valued and respected his experience.

We kids, though, didn't have much time for that stuff. We just wanted to be, well, kids—mischievous, impish and high-spirited. But so did Robbie. He had more mischief in him than a common room full of Slytherins. He could fool around with the best of us. He might have had the mind of an adult, but he truly had the heart of a child.

Robbie was always looking to lighten the mood and make us laugh. My earliest memory of him was at the table read before the first film started shooting. It was intimidating, 40 or 50 of us all sitting around a massive table to read through the script for the first time together.

Before we started, we all introduced ourselves: "I'm Dan, and I'll be playing Harry Potter." "I'm Tom, and I'll be playing Draco Malfoy." Robbie and Emma were sitting side by side. When their turn came, he persuaded her to swap characters. "I'm Emma and I'll be playing Rubeus Hagrid." "I'm Robbie and I'll be playing Hermione Granger." We all giggled into our scripts as this huge, friendly, charming, smiling man reminded us with that one little joke that we should approach this endeavor with a sense of fun. We were only making a film. We weren't saving lives.

That's not to say he wasn't a true professional. Robbie knew how important it was to know your lines, to be on your mark, to play to camera. We learned our trade from watching him. He set a great example to us all on how to nail the basic skills of being on set, but never in a boring or patronizing way. Although he routinely had to deal with a crazy amount of hair and make-up and suits and stilts, he still somehow managed to create an environment that allowed us all to be playful.

And Robbie was endlessly playful. He was constantly cheeky. Most of all he was always kind. He never took himself too seriously—and these characteristics lay at the heart of everything, I think, because if Robbie took himself too seriously, if he forgot what it meant to be kind, there would have been no Hagrid.

Without Hagrid, there's no Hogwarts. And nobody could, would or ever will play that gentle giant half as well as my dearly missed friend Robbie Coltrane.