Gerard Butler insists the sequel to 'Olympus Has Fallen' will be ''pretty insane''.

The '300' actor - who will reprise his role as secret service agent Mike Banning in 'London Has Fallen' - claims it will be a struggle to make it as good as the original, but is convinced they'll be able to do so.

He told ''That ['London Has Fallen'] was one that kind of came out of nowhere. The first one ['Olympus Has Fallen'] was pretty insane and it's the same with this. How do you top that? But that's what we are trying to do right now.''

Although Butler, 44, is yet to start filming the movie- which is due out in October next year and also stars Morgan Freeman and Aaron Eckhart - he let slip that the plot will be just as thrilling as the previous instalment.

He said: ''It's about a terrorist attack in London and the president is over there because there's a funeral for the British Prime Minister which is part of the plot to get everybody who is anybody to London. Then the s**t hits the fan.''

Meanwhile, Butler's latest movie 'How To Train Your Dragon 2' opened in cinemas this week.

The hunky actor - who plays Stoick the Vast in the new animation - recently described making the children's movie as ''beautiful exhilarating experience''.

Talking on US chat show, 'Late Night with Seth Meyers', he said:''It's good fun making an animated movie. Especially when you do your thing, your voice, then you let it go. It took a while, it was three years in the making, then I'm like an audience member and I turn up and I'm blown away. It's such a beautiful exhilarating experience.''