Death of Varenne prompts outpouring of tributes from across Italian sport.Varenne, widely regarded as the greatest trotting horse of all time, has died in Italy at the age of 31.  The champion, affectionately known as "il Capitano" (the Captain), passed away on Monday night at the LJ stud farm in Eboli, near Salerno, where he had spent the final period of his life.   The horse's official Instagram page announced the news, stating that a veterinarian had confirmed the cause of death as a sudden heart attack, and paid an emotional tribute asking him to "fly free" and reuniting him in spirit with his late owner, Enzo Giordano.   Varenne was born on 19 May 1995 at the Zenzalino stud in Copparo, near Ferrara in northern Italy. He was bought by Enzo Giordano for around 180 million lire and went on to win 62 of the 73 races he contested, earning his owner more than €6 million in prize money.   Varenne's crowning achievement came when he completed the European Grand Slam twice, in 2001 and 2002, sweeping the three most prestigious Group 1 races in Europe: the Prix d'Amérique, the Gran Premio Lotteria and the Elitloppet. He also set a world record over the mile in the US and triumphed at tracks from Paris to Stockholm to New York. Varenne ran his final race on 28 September 2002 in Montreal, finishing second in the Mondial Trot behind the French mare Fan Idole before being demoted to last place for a gait infringement. After retiring from competition, he enjoyed a long second career as a stud, siring more than 3,000 foals.   Tributes have flowed from across the sport. Giampaolo Minnucci, his long-time driver, said "history was written by him - I just followed behind," adding that he owed his own public recognition entirely to the horse and would be grateful to him for the rest of his life.   Daniele Giordano, who inherited ownership of Varenne following his father Enzo's death last year, described losing not only the greatest trotter in history but one of Italy's great legends, one whose fame reached far beyond sport.