And while I'd be the last person to undervalue the books and performances which made the series so winning, plenty of other kids' movies started with beloved best sellers and star-studded casts that just couldn't be sustained.
So how did the Harry Potter series manage to maintain its quality and the commitment of its audience? I've visited the set several times and come to the conclusion: They broke most of the rules of movie-making. And many of the Potter rules of success could be used in others' business.
1. Improve collegiality
The whole series had one over-arching producer, David Heyman, who worked with four directors - all of whom shared their knowledge and insights with each other. "Chris spent time with Alfonso," Heyman reflected. "Alfonso spent time with Mike and Mike spent time with David, showing him an early cut of the film, talking through what it means to be a director and how they went about it and any sort of titbits that they can pass on. And it's a really collegial and supportive environment between directors."
2. Keep a good team together
Of course, many of the actors remained the same. But they were also long-time colleagues, many of them graduates of RADA (Royal Academy of Dramatic Art.) So the fantastic training and experience of the cast set a standard. Moreover, they didn't just turn up for the day but were well known to one another, having worked together on different projects for years. Mutual trust matters; it means you can start on a basis of trust and share a language you don't need the time to develop.
3. Favor permanence
This isn't a word you hear very often, either in the film industry or any other industry these days. But many of the designers, sculptors, painters and runners spent years working together on these films. When I visited the set on several occasions, they all commented on how much they appreciated not just continuous employment but long-term commitment to a project that didn't change or collapse after a few months. It inspired ever higher levels of perfectionism in their work. "It's not," one sculptor told me, "just because it's the first time I ever got to work indoors! I'm psyched that I'm surrounded by people who do great work and I won't want to let them down." You don't get this when everyone can be cast out tomorrow.
4. Respect and honor the customer
Another remarkable comment I heard often concerned the audience. "You know how much these stories mean to kids. That means you have a lot to live up to." What made this remarkable is that it is rare in the movie business for anyone to think about viewers - with respect. But on this movie, most contributors had, or knew, kids for whom these stories were magical. They were proud of their association and wanted to be able to show their work with pride.
What's intriguing and ironic is that, for the last 20 years, the movie industry has regularly been cited as an example of how quickly, effectively and cheaply teams can be assembled and abandoned. But the Harry Potter series has gone from strength to strength because that is not the way that it worked. Instead, like-minded people were brought together for years, instilled with pride in their work and long term commitment to each other.
Could that model of work ever catch on?