But for some it was the Potter kids that stole the show. One conference-goer had this to say:
"I loved that they so embodied their characters. Not just playing roles, but in a way it really did feel like they walked out of the movie and into the con."
"Young Snape [Benedict Clarke] was walking around at the ball in a Slytherin tie. Young Sirius [Rohan Gotobed] was wearing a shirt that said 'I spent time in Azkaban'. Rose [Helena Barlow] kept answering questions very diplomatically, in a very Hermione-like way. I couldn't get over it. It really felt as though they WERE the characters, not just actors in a film."
Will Dunn [James Sirius Potter] tweeted: Absolutely loved the signings, and the Q&As, fans were awesome, Melissa Anelli and everyone else did a great job :)
Benedict Clarke added: The Q&A and HP trivia, running on stage and dancing with the other actors at the ball, the Chinese Fireball rollercoaster :)
You can follow all the young Potter stars on Twitter:
Arthur Bowen | Benedict Clarke | Will Dunn | Ryan Turner | Ellie Darcey-Alden | Rohan Gotobed