Ben Barnes, who plays the title role Prince Caspian, said he was so overexcited that he was "babbling like an idiot".
"This is the pinnacle, it's the climax," he said.
"Despite all the people behind me I can guarantee I'm the most excited person here."
He added: "I still find it difficult to watch myself because it's difficult to suspend your disbelief enough to see a prince and not yourself but hopefully everyone else will see Prince Caspian and I think it's a really exciting, engaging film."
Director Andrew Adamson said: "People say not to work with children but I highly recommend it.
"They energise you, on those days on set when you're tired, they are not. They give you the energy back."
Stars including Ben Barnes, who plays Prince Caspian, mingled with fans
Little Britain star David Walliams, who voiced the Bulgy Bear character, said: "It's great to be part of something as epic as this, something where you've grown up reading the books."
The second instalment of The Chronicles, based on the bestselling books by CS Lewis, promises to take audiences on an "extraordinary" journey back to the magical land of Narnia.
Film studio Disney claim the sequel is "bigger and more spectacular than ever before", with more action scenes and visual effects.
The pedestrian area surrounding the O2 arena was transformed into a Narnia world, with fighting knights and horseback sword performers entertaining fans and celebrities.
The Chronicles of Narnia: Prince Caspian is released in UK cinemas on 26 June.
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