World champion David Haye led the tributes to boxing great Sir Henry Cooper, who died on Sunday at the age of 76.
Cooper, a former British heavyweight champion, died just two days before his 77th birthday.
He passed away at his son's house at Oxted in Surrey.
Haye, the WBA world heavyweight champion, was joined by former world heavyweight champion Lennox Lewis and Manchester United and England striker Wayne Rooney in posting tributes on Twitter.
Haye wrote: "One of Britain's greatest sportsmen Sir Henry Cooper passed away today. A true warrior and great human being. Rest in Peace."
Lewis tweeted: "R.I.P. Sir Henry Cooper. Former British, Commonwealth and European Champion. My deepest condolences to the Cooper family."
Rooney added: "R.I.P Sir Henry Cooper, just heard now, didn't know. One of Britain's all time greats. Gutted, deepest sympathy to his family. Such a sad day."
Sir Henry, who was knighted in 2000, is best remembered for two famous clashes with Muhammad Ali in the 1960s.
He floored Ali - then known as Cassius Clay - in the fourth round with 'Enry's Ammer' - his trademark left hook - but Ali eventually won the 1963 non-title fight at Wembley.
Ali triumphed again when they boxed three years later but Cooper remained a favourite with the British public.
Robert Smith, the general secretary of the British Boxing Board of Control, paid tribute to Cooper tonight and described him as "one of the sporting icons, not just for the boxing public but sport in general".
Speaking to Sky Sports News, Smith continued: "He fought Muhammad Ali twice, once when he was Cassius Clay and once when he was Muhammad Ali, and he put up wonderful performances.
"Ali is possibly the greatest athlete there's ever been and Henry put up a great performance and just wasn't quite good enough on both occasions - but he's not the only one who wasn't good enough to beat Ali.
"Ali was one of the first 'big' heavyweights and Henry lost to Joe Bugner, who was 15-odd stone and Henry was 14 - just bigger men. For such a small man, he put up some great performances in a world-class context."
On the affection in which Cooper was held, he added: "It's not just the boxing and your ability, it's the personality as well.
"He won the BBC Sports Personality of the Year on two occasions, which is a tremendous feat for a boxer. Everyone called him 'Our Enry', and he was much loved, he served boxing wonderfully."
Johnny Nelson, the former WBO cruiserweight world champion, was shocked by the news.
Nelson told Sky Sports news: "Henry was a total champion. He was always a gentleman, always straight down the line. He told it how it was.
"Ali always showed that bit of respect for Henry Cooper. Everybody in Britain: be proud of what he achieved and what he actually did.
"He was a no-nonsense fighter, the man that almost dethroned one of the greatest fighters in the world, Muhammad Ali.
"There's nobody that came across Sir Henry that had a bad word for him."
The Sun's boxing writer Colin Hart echoed those thoughts and said: "He never changed, he had the same size in hats and was the same 'Our 'Enry' - he was popular from Land's End to John O'Groats.
"There was a famous boxer called Gentleman Jim Corbett and I think, if he hadn't been Sir Henry, we could definitely have called him Gentleman Henry Cooper."
Hart, talking to Sky Sports News, looked back on the most famous nights of Cooper's career and said: "He was more famous than anything else for putting Cassius Clay on his backside with that great left hook of his at Wembley. That was Ali in his prime.
"In the first fight, if that round had lasted another 10 seconds, there's every chance Henry would have changed the course of history. If he'd won, then Cassius Clay wouldn't have fought Sonny Liston in his next fight for the world title."When they fought again Ali was aware of the left hook and didn't give Henry a chance to use it, and on both occasions Henry lost on cuts.
"I'm sure Ali will shed a tear when he hears the news tonight. I was very lucky, I covered a lot of Ali's career and whenever I arrived, his first question was always 'How's Henry Cooper?'. That rapport and friendship were never broken."
Former world featherweight champion Barry McGuigan, a personal friend of Sir Henry, said he never recovered from his wife's death in 2008.
He said the couple were "devoted to each other" and were a great example.
He told BBC News: "It's tragic news for the world of boxing. The great Henry Cooper, and what a great man he was."
He said Sir Henry encouraged him when he got into boxing, adding: "All you ever got was 'Son, you've got great potential'. He was full of encouragement, he was a really lovely man.
"He was the first boxer to be knighted and to my mind that's the greatest compliment of all."
He said he never weighed more than 190lbs and was giving away weight to the likes of Ali.
He continued: "I have absolutely no doubt had he been around in this day and age he would have been the world cruiserweight champion for a very long time."
Promoter Frank Warren told Sky Sports News: "He transcended boxing, he was a true gentleman of sport and had a huge place in the public's affection.
"He never won the world title but he had true British grit, he tried.
"He fought Cassius Clay, who was this brash young kid coming over, and he put him on his backside and went into British sporting folklore. His weakness was that he cut very easily, and he got cut in both those fights."
On Cooper's enduring appeal, Warren added: "He wasn't an extrovert like a lot of fighters in this day and age, saying what they're going to do - he was unassuming and in his time he was a superstar, he became a bit of an icon.
"For generations of people who'd never seen him fight, a legend built up and the public took him to their heart because he was such a gentleman."