British actor James Corden caused a security scare at a London airport as Prince William and Catherine, Duchess of Cambridge returned from their first official trip to New York after mindlessly wandering into a blocked off area of the runway.

The star, who features in new Disney movie musical Into The Woods, reveals he found himself sitting in the same first class cabin as the U.K. royals when he was flying home earlier this month (Dec14).

He says, "I don't normally fly first class on aeroplanes, I've never done it, but because I'm in a Disney film, that's what happens...

"So I'm in the plane, and I'm on the plane with William and Kate (Catherine) in the same cabin... My first thought was, 'If this plane goes down, no one mentions that I've died...!' It's just, 'They died... and 200 other people...'"

Corden claims he and one fellow male passenger were the only others in first class not travelling with the Duke and Duchess, so he was inadvertently led astray as he exited the plane upon arrival in London.

He explains, "I'm going off the plane, I'm listening to (music) in my headphones and I'm very happily wandering along. As I'm getting off the plane, this side door opens and the people in front of me go in through the door, and so I just go through the door and I'm going down these stairs and then I'm on the runway, on the tarmac, with all these cars and I'm thinking, 'Wow, Disney have really... looked after me on this trip...!'"

However, Corden soon discovered the waiting vehicles were not meant for him and he was flagged as a royal security risk.

He continues, "Then this arm goes (stops me) and (the bodyguard) goes, 'What are you doing?' I'm like (taking my headphones out), going, 'What?' and he went, 'What are you doing here?' And I just went, 'I'm in a Disney film. I'm the lead in it, I think it's probably... one of these cars are mine.' And he goes (speaks into a microphone in his sleeve), 'We've got a 526 down on the tarmac'. I go, 'No no, I'm not a 526, honestly, I'm not a 526. I don't know what a 526 is, but I'm not it.' He goes, 'Sir, you're gonna have to go back up the stairs and go back to the top."

Corden followed the instructions, but was stopped again by another bodyguard moments later.

He says, "I go back up the stairs (to the main airport terminal), and then this hand goes, (stops me again) and (a guard) goes, 'What are you doing in the stairwell?' (I said), 'I don't normally travel in first class and I got a bit confused...' and he goes (speaks into his sleeve mic), 'We've got a 526 in the stairwell.' I'm like, 'Honestly, I'm not a 526!'"

The plane drama has since convinced Corden to talk up his royal encounter by suggesting the trio "slept together".

He exclaims, "For all of that (drama), I can legitimately say that I've slept with the future king of England. There's no denying it; I slept with him. In fact, we all slept together! The three of us slept together one night, coming back from New York, it's no big deal, get over it!"