They came in capes, Gryffindor colours, elf masks, ginger wigs, and with the famous lightening scar felt-tipped across their head.
I wasn't in costume, but I understood them.
I understood why they'd camp out for four days, amongst the lingering pigeons of Trafalgar Square and the pesky English summer rain, to see the stars of Harry Potter.
They weren't there for a glimpse of celebrity like the usual film premiere crowds, they were there for something far more touching.
"They haven't come to see us really, they've come to say goodbye to their childhood," Jason Isaacs told me on last night's red carpet.
And he was right - for me and millions of other fans across the world the final Harry Potter film marks the end of a magical tale that we have grown up with.
From JK Rowling's legendary books, which left us spellbound and reading under the covers by torch light, to the cinematic phenomenon that followed, Hogwarts has been a part of our lives for as many years as we can recall.
Remember those cute pictures of Daniel Radcliffe, Emma Watson and Rupert Grint looking angelic on their first day on set, or at their first premiere? I was also that small when the camera lights started flashing, cementing their now internationally recognisable faces in film history.
I can still picture the day I got my hands on the first Harry Potter book, The Philosopher's Stone, I was 9 years old and it was all anyone at school could talk about. What I don't remember is what came before Potter, nothing from those years leaps out from the page quite like platform nine and three quarters, Albus Dumbledore, Quidditch or the terrifying Lord Voldemort.
So for me and many others who have grown into adults with Harry, Hermione and Ron being around, Harry Potter and The Deathly Hallows Part 2 is not just the finale of a film series that has broken box office records, for us it's the end of a narrative that has helped shape our imaginations and heightened our expectations.
Last night was a fitting tribute to this. There were tears in the crowd's eyes before the cast had even arrived. Clips of the film being shown on a gigantic screen were enough to illicit screams that could be heard on the other side of town.
I made my way to the top of the stars in Trafalgar Square that looked down onto the thousands of dedicated, cheering, Potter followers and tried to soak in just how Daniel, Emma and Rupert would feel when they stepped out of their shiny cars to this.
Here in this historical setting, at the foot of Nelson's Column, a final piece of Harry Potter history was being made.
Right on cue, the weather cleared and the sun shone through just as the stars arrived. A whole new level of frenzy erupted and over the next three hours the cast of Harry Potter, young and old, spent time with their loyal fans.
Eager to please, they signed books, t-shirts, limbs and posed for snaps for hours on end.
The stars have remained humble to this day and they were not shy of letting their emotion show, Both Emma Watson and JK Rowling shed a tear on stage and Rupert told me he would be crying after a glass of bubbly.
It was touching to see that, despite their global adoration, they remain appreciative of such a phenomenal experience. Emma even claimed she doesn't think she "will ever attend anything like this again in her lifetime".
As I finally got my chance to speak to the cast they spoke of the sadness and grief they felt now that it has all finally come to an end. But they also spoke of great pride, triumph and a sense of achievement.
Just like the end of the final Harry Potter film, the end of the last ever world premiere did not disappoint.
For now we bid farewell to Daniel, Emma and Rupert, who may not have started out as great actors, but who brought my childhood friends to life. For that they've earned a place in my heart and I wish them all the best.