McCullough gave him one of the top three fights of his career and almost quit on his stool after the 9th round (according to Ring magazine). In October 2000, McCullough was to return to his native Belfast for a homecoming fight. Two days before the fight was scheduled to take place, he was told that he had a cyst on his brain, he couldn't fight again and that one more blow to the head could kill him. McCullough flew back to Las Vegas and was advised by the Nevada Commission to visit the neurosurgery department at UCLA for a more thorough investigation. Within a few weeks the doctor at UCLA, Neil Martin, called to say he had consulted with some of the top neurosurgeons in the US and they had come to the conclusion that the cyst was not on his brain, but in a space between the brain and the skull – called the arachnoid mater – and that he saw no reason for him to give up his boxing career. Nevertheless, the British Boxing Board of Control (BBBC) continued to deny him a licence. He was relicensed in Nevada and fought again in January 2002. After a very public battle, the BBBC could no longer deny him a licence and later that same year McCullough stepped back into a British ring under the Frank Warren Promotions banner. Thereafter he had mixed success, winning five fights but losing to Scott Harrison and Mexican world champion Óscar Larios on two occasions. The result of his first fight with Larios is widely disputed. On 17 August 2005 McCullough was appointed the first WBC World Ambassador for Peace and Goodwill in Sports. In September 2005, McCullough became a United States citizen. In November 2005, McCullough released his autobiography, Pocket Rocket: Don't Quit, in the UK and Ireland. He went on a publicity tour to promote the book, which reached Number 2 on the best sellers list. In 2007, McCullough joined the Ultimate Fighting Championship organisation as a PR associate, to promote Mixed Martial Arts (MMA). He currently trains fighters both in boxing and MMA and is setting up his own charity – IHOW. McCullough vs. Martínez In 2007 McCullough signed to fight Spain's Kiko Martínez who had just defeated Bernard Dunne at the Point Depot, Dublin for the European super bantamweight title. The fight between McCullough and Martínez was due to take