© Ben Sutherland/Flickr

Two internet pranksters broke into the National Theatre and spent the night in the venue after finding a door unlocked on a balcony.

Ally Law, who uses YouTube to post videos of himself performing reckless stunts, managed to sneak into the theatre at 10pm on a Saturday night. Law and his accomplice avoided security, climbed onto the roof of the National Theatre, and found an unlocked door.

From there they spent the night in the empty theatre, heading into the Olivier Theatre and climbing up the stage's fly tower and lighting rig, surrounded by the set of Follies.

Other videos on Law's YouTube channel feature him spending the night in a trampoline park and practicing parkour.

Liz Fosbury, chief operating officer at the National Theatre said: "The safety and security of everyone at the National Theatre is of the utmost importance. We were shocked and concerned that two intruders recently put themselves at great risk by gaining unauthorised access to a restricted area of the building.

"We would like to reassure audiences that we have taken immediate action to further strengthen our security, we liaise with the police on an ongoing basis and we are working closely with the Met following this incident."

Law posted underneath the video that it was "reckless of us not to check the bars beforehand." In the video, Law explains that his camera had recently been confiscated by the police.