Heath Ledger's turn as Batman's archenemy, The Joker, is lauded as one of the most iconic movie performances of all time. But did you know that director Christopher Nolan included a subtly touching tribute to the late actor in the final instalment of his Dark Knight trilogy?

Ledger's performance as The Joker undoubtedly contributed to the consensus that 2008's The Dark Knight is the strongest film in the trilogy, and one of the best superhero films of all time.