For a moment I wondered whether this was to be a black comedy of failure - a film shot over 10 years where the only thing that showed tangible change was the length of Gilley's hair.
At first, whatever Gilley did seemed to go disastrously wrong. Having worked tirelessly over two years to get the United Nations on board, he secured a meeting with then UN Secretary General Kofi Annan. Annan agreed that there would be an announcement of the UN's decision to give World Peace Day its full support - at last Gilley would achieve the publicity he needed to push the campaign forward. The press conference was scheduled for the morning of September 11, 2001 in New York. Due to the catastrophic events of that morning, it never took place.
When the campaign was not being sabotaged by terrorism, it was undermined by Gilley's own naivety. He decided to film messages of support from all the world's surviving Nobel Laureates, and took his video message to the 22 delegates of the Arab League in Cairo. He played the video. As Israel's Shimon Peres announced his support for a day of peace you could have cut the atmosphere with a scimitar.
The Palestinian representative was enraged, saying: "By showing Mr Peres, who takes part in daily killing in Palestine, this film is biased towards the enemy. There is no reference to the Palestinian children killed at checkpoints."
Gilley protested that he had attempted to interview Yassir Arafat for the video but to no avail. But his quest for a day of world peace was turning into an expensive disaster.
He was nothing if not persistent, and quickly learned from his mistakes. He requested another interview with Arafat. It was granted but the Palestinian president died before it could take place. He travelled to Israel in the hope of obtaining an important Palestinian to back his campaign. Eventually he succeeded - the Palestinian Minister of Detainees spoke in Hebrew to the camera.
Gilley had not forgotten the lesson of balance either. Ordinary Israelis added their messages - memorably a soldier who said that he looked forward to the day when he would be able to throw his weapon into the sea.
Gilley also began to become savvy to the publicity game. He attempted to recruit big names. Angelina Jolie sat in the living room of his mother's house and offered to do a promotional press conference. Jude Law turned up for promotional work. Gilley mentioned that he planned a trip to Afghanistan. By the end of the session, Law had agree to accompany him.
The campaign gained momentum. Gilley and Law toured Afghanistan with flak jackets and a military escort. The British made the right noises and, crucially, the Taliban representiatives pledged that they would not interfere with Unicef's proposed vaccination campaign planned for September 21, 2007 - the first World Peace Day that had been heavily promoted.
On that date, Coke placed a message about World Peace Day on their bottles; 1.4 million children were inoculated peacefully in Afghanistan. Food drops were made in Sudan and the day was observed by leaders in Israel and many other countries. In the Royal Albert Hall, Annie Lennox rallied the faithful with a charity concert.
Had Gilley achieved his aim? Well he certainly saved lives, he provided respite to suffering people, he ignited a small spark of hope and raised consciousness. For one small-time film maker, that's plenty.
He invited more than 2,000 people from relevant organisations and the world's media to his launch event at London's Globe Theatre. Just 114 turned up - all of them Gilley's mates.