In our continuing series, IBTimes UK takes a look at the work of British director Christopher Nolan in the lead up to the November release of his ninth film, Interstellar. This week we look (in two parts) at The Dark Knight, Nolan's most adored and successful film to date.

Christopher Nolan's films deal with damaged men ravaged by personal demons. Following, Memento, Insomnia, Batman Begins and The Prestige all embody this concept but not one better than the director's greatest triumph, The Dark Knight.

Batman Begins was a fine film but still recognisably a superhero movie in terms of structure and feel. It was darker but there was a trepidation about it and a potential that wouldn't be realised until three years later.

Initially reluctant to return for a sequel, Nolan eventually signed on because of the allure of an iconic villain he teased at the end of Batman Begins: The Joker. Heath Ledger's unforgettable performance as The Joker was a key part of the film's success but we'll get to that in part two.

The Dark Knight succeeded because it was the perfect representation of the idea that superhero movies could take themselves seriously and flourish. It is not really a superhero movie at all but a crime epic akin to The Godfather or Heat, which Nolan regularly cited as a key influence on his and brother Jonathan's script.

The Dark Knight
Batman on the film\'s new vehicle, the Batpod Warner Bros

Like Heat, and as ever with Nolan, this is a film about duality, but here that theme runs rampant, popping up in numerous ways. There's the duality between Batman (Christian Bale) and the Joker, and Batman and Harvey Dent (Aaron Eckhart).

Batman and the Joker are two intrinsically linked people hidden behind masks, dealing with mental scars with larger-than-life personas to either fight crime or dish it out. In Harvey Dent, Bruce Wayne sees a way out of his life as Batman, he sees the hero Gotham needs to save it, the hero he can never be behind Batman's cowl.

There are internal conflicts, too, between Bruce Wayne the man and Batman the symbol, then later in the film between Dent and the murderous psychopath he becomes after losing everything.

On a broader scale, The Dark Knight is about the battle between right and wrong. Visually this is represented partly by Dent's trick coin, which when burned and scarred in the warehouse explosion that kills Rachel Dawes (Maggie Gyllenhaal) causes the mental breakdown that unleashes his hidden darkness and creates the villain Two-Face.

In a more comprehensive way, though, Wally Pfister's Oscar-nominated cinematography represents this theme, casting daytime scenes in stark brightness that juxtaposes the night time scenes steeped in shadow. This reflects the struggle between right and wrong, good and evil, the White Knight represented by Harvey Dent and the Dark Knight represented by Batman.

The Dark Knight
Heath Ledger as the Joker in the iconic interrogation scene Warner Bros

Another key theme of The Dark Knight is theatricality and the showiness of its three lead characters. We see this in each of their first scenes: Batman crashing his Batmobile through the side of a car park as a distraction; Harvey Dent's show of fortitude in court; and the Joker in both the gas grenade he puts in the bank manager's mouth and the now-famous vanishing pencil trick.

Everyone is putting on a show to make their point. Batman and Joker to inspire fear, Harvey Dent to convey the fearlessness that masks his inner darkness. The Joker remains an absolute throughout the film – the personification of utter evil – but the other two eventually find their facades torn down. Batman must lose the theatricality and fight ever-more desperately, while Dent's downfall is at the very heart of the film.

Each of the film's heroes eventually find themselves unable to commit to their idealistic goals, in the end turning down dark paths to ultimately do the right thing. Each and every "good" character does this, creating lies to conceal devastating truths, which fits with the grander Nolan theme of complicated men hurting those around them.

Lies are another prevalent theme of the film, coming to the fore when the lines between good and evil are blurred. Dent's coin is initially a lie until horrific acts make it an agent of the fairness Joker claims chaos to be; Alfred (Michael Caine) burns the letter that would break Bruce Wayne's heart in the hope of keeping his optimism alive; and Jim Gordon (Gary Oldman) fakes his death for the sake of his family's safety.

Biggest of all is the lie that ends the film, as Batman and Gordon agree the former must take the blame for Dent's crimes so the city's White Knight can remain so in the public eye and keep those he's imprisoned behind bars.

The Dark Knight
Batman takes on a SWAT team during the film\'s climax Warner Bros

Batman crosses another line earlier, when - following the Joker bringing Gotham to its knees - he turns the city's mobile phones into a sonar mapping device in a desperate effort to find the Clown Prince of Crime. The difference between all these bad acts and those of the Joker and later Two-Face however, is that they are tinged with optimism.

Alfred burns the letter because he thinks it is best for Bruce, Gordon fakes his death to protect those he loves, and Batman's sonar mapping comes with a clause. Only Bruce's friend Lucius Fox (Morgan Freeman) – who is apprehensive of the line being crossed – can control it but the faith Wayne puts in him is rewarded after the Joker is found and the machine destroys itself.

During the Joker's rampage, optimism in Gotham is crushed and nearly wiped out entirely but Batman and Gordon keep it alive with a lie, as does Alfred with Bruce, leaving the film on a hopeful note that ultimately serves as proof that the Joker didn't really win at all.

In part two, we'll look at the film's various performances and its place in Nolan's Dark Knight Trilogy.