Three-time world heavyweight champion Muhammad Ali has died at the age of 74 after he was admitted to hospital earlier in the week with a respiratory condition.
Ali, who was diagnosed with Parkinson's Disease 32 years ago, is widely considered to be the greatest in boxing history.
"Not just boxing but the world has lost an iconic figure," promoter Frank Warren told Sky News.
"He called himself the greatest and if he wasn't the greatest, he was certainly one of the greatest boxers of all time.
"Not only that, he crossed over to the general mainstream public. He became bigger than sport and was probably one of the most recognisable people on the planet.
"What he did for his own race - being a black American - he stood up against the war in Vietnam to the detriment of his career and his life. I think at the time he was out of the ring for three years and was sentenced to five years in prison, which he appealed. To do that shows how strong his belief was.
"He probably paved the way for (Barack) Obama to be the president of America."