The new Lance Armstrong documentary The Armstrong Lie is now in cinemas. Harry Guerin finds out whether it has crossover appeal.

During one of his many forays into the complexities of the human psyche, Seinfeld's George Costanza brilliantly summed up dishonesty with the following gem: "It's not a lie if you believe it."

It's a line that comes to mind repeatedly while watching Alex Gibney's (We Steal Secrets: The Story of WikiLeaks, Mea Maxima Culpa: Silence in the House of God) The Armstrong Lie, a film with plenty for both the cycling devotee and the person who only knows the outline of the scandal.

Gibney originally began making a film with and about Armstrong in 2009 - "his comeback year" - and had amassed interview and training footage in the build-up to his Tour de France return. He then followed Armstrong right from the starting line that summer to the finish in Paris, but as the doping scandal and investigation gathered more momentum Gibney shelved his footage, thinking that the film was dead.

However, following Armstrong's tell-all interview with Oprah Winfrey in 2013, Gibney resurrected the project, went back to interview Armstrong again and framed his film in the context of the events of 2009 and the question that he felt haunted both himself and his subject: Why had Armstrong come back?

With so much detail to get through, it's a testament to Gibney's skill as a director that The Armstrong Lie is never slow-moving and plays better than a lot of thrillers. It is tightly edited, sharply scripted and has brilliant footage - from blood tests to home movie memories - throughout. While Gibney wanted one question answered, he raises far more in the minds of the viewer - about strength and weakness, hope and despair, our need to create heroes and whether Armstrong has become a haunted man or remains one whose survival instinct is still so finely tuned that he is, as a contributor puts it, trying to manage his own storyline. Could there really be a fifth act in this American life?

Three people who should have been asked and who are absent from Gibney's interviewee roster are former teammate Floyd Landis, whistleblower and onetime Armstrong soigneur Emma O'Reilly and journalist Paul Kimmage - we hear the latter at a press conference but do not see him. Their inclusion, at the expense of some of the 2009 footage, would've elevated The Armstrong Lie from good to great. As, indeed, would more present-day screentime with Armstrong in order to get a better sense of what he sees as his future.

While the lie is over, we await the Ben Foster-starring biopic with even more interest.