Kauto Star\'s legendary career came to an end on Wednesday when the dual Cheltenham Gold Cup winner, described as a \"once-in-a-lifetime horse\" by his trainer Paul Nicholls, was retired. Kauto Star, regarded as one of the greatest horses in jump racing history, won the Gold Cup in 2007 and 2009 and made history by claiming a record fifth King George VI Chase last year. The 12-year-old, the only horse to have regained the Gold Cup having lost it, pulled up when going for a third victory at Cheltenham in March and owner Clive Smith and Nicholls decided to put him into retirement after meeting on Wednesday. \"We\'ve decided to retire Kauto Star as of today,\" Smith told BBC Sport. \"I\'d always thought he had done enough. He\'s had a magnificent career and I\'m mighty proud of him. \"It\'s been the journey of a lifetime. He\'s a wonderful, wonderful horse and a good friend of mine.\" \"The end of an era has finally arrived,\" said Nicholls in his Betfair column. \"Don\'t get me wrong, Kauto looks and feels as vibrant as ever, as those who saw him at our owners\' open day last month would testify to. He was mad fresh that day and continues to be as alert as ever and very, very well in himself. \"But I suspect Kauto will be like that when he is 20-years-old.\" Kauto Star originally looked set for retirement in 2011 after being pulled up at Punchestown. But, after several months from racing, he returned to win at Haydock in November before his record-breaking success at King George. \"Kauto is signing off in full health and after a season in which he proved so many people wrong by winning a fifth King George and a fourth Betfair Chase, to add to his two Cheltenham Gold Cups and Tingle Creeks,\" said Nicholls. \"Who wouldn\'t want to train a horse of this quality any more? He is a once-in-a-lifetime horse, after all,\" he added. \"Ever since he won on his debut for me at Newbury on December 29, 2004, the horse has consistently proved himself a class apart. And a £1m Betfair Million bonus in 2007 and 16 Grade One wins later, who would bet against him going to Kempton in December and making it number 17? \"But sometimes, you have to listen to your head and your heart, and both told me that retirement was the only option.\" Kauto Star, known as \'the extra-terrestrial\' in his native France, takes his leave of jump racing having earned almost £2.4 million ($3.76 mn) during his stellar career.