Heath Ledger's unscripted Joker moment in The Dark Knight led to iconic scene

The late Heath Ledger tragically died at just 28 before The Dark Knight had even hit cinemas and went on to posthumously win him an Oscar for his role.

Locking himself away for days in a hotel room to create his take on 's Clown Prince of Crime, the star took the part in Sir Christopher Nolan's blockbuster sequel incredibly seriously.

Through his method, he brought some unscripted moments that made it into some of the movie's most memorable scenes.

One of these included the brutal pencil trick when the villain crashes a mob meeting.

Approached by a thug, Joker says, "I'm gonna make this pencil disappear" before slamming it through a guy's head and casually quipping, "Taa-daa! It's gone!"

Although the stunt was choreographed with a stuntman without the use of CGI, the exact timing was Ledger's and his delivery was improvised. Another unscripted moment that made it into the movie was Joker's sarcastic slow hand clap for Jim Gordon from his prison cell. And most famously, there's a one-take hospital explosion scene when the villain is dressed as a nurse.

As is classic with Nolan, the Oscar-winning director wanted to blow up a hospital building for real rather than use CGI. The only problem was that when Joker hit the button, there was a delay on the trigger, and so Ledger stayed in character, trying to get it to work until it suddenly exploded behind him in a perfectly improvised sequence.