Singling out one horse as the greatest thoroughbred of all time has been the source of much heated debate over the years. While some critics look to the distant past for their top competitors, others argue that victories achieved in a modern era when competition is especially fierce, are worth more.
Of course, no greatest-ever list can be definitive, even if it's hard to argue against actual results. However, it's hard to dispute the inclusion of some horses in such lists. Here, in no particular order, are just a few thoroughbreds widely-regarded as the best horses that ever raced:
1) Arkle: Even though his career was cut tragically short by injury, Arkle managed to achieve more in just a few short years than most horses ever manage. With Pat Taaffe in the saddle, the Irish bay gelding won three Cheltenham Gold Cups, as well as an Irish Grand National, the King George IV Chase, the Hennessy Gold Cup and a host of other major races.
In the space of less than 18 months in the mid-1960s, Arkle established himself as one of the greatest steeplechase racers of all time, a status he still has to this day. Indeed, his Timeform rating of 212 is the highest ever awarded to a steeplechaser.
2) Best Mate: Another Irish steeplechasing legend, Best Mate matched Arkle's feat of winning three Cheltenham Gold Cups, racing to victory in 2002, 2003 and 2004. The English-trained bay gelding also won the 2002 King George VI Chase and a number of other major races, earning him a place in the sport's history.
In all, from 22 starts, Best Mate came first 14 times and second seven times. The horse was honoured with a place in the Cheltenham Hall of Fame, with a statue also erected in his honour at the famous course.
3) Nijinsky: As the only horse to have achieved an English Triple Crown (winning the 2,000 Guineas, the Epsom Derby and the St Ledger Stakes in a single season at the age of three-years), since the end of the Second World War, Nijinsky will always have a place in racing history.
However, the Triple Crown win was just one of the horse's many accomplishments. He also enjoyed a glittering career in Continental Europe, winning dozens of big races between 1969 and 1970. Even after he'd retired form racing he was still a star, becoming the leading sire of Great Britain and Ireland, with several of his offspring going on to top the earnings charts at the end of the racing season.
4) Secretariat: To many simply the greatest sprinter that ever raced, Secretariat won 16 of his 21 career starts, including some of the biggest events in world racing. Above all, the stallion made his name through his exploits in the US Triple Crown, romping to convincing victories in the Kentucky Derby, the Preakness Stakes and the Belmont Stakes.
The chestnut stallion is considered to be one of the greatest athletes in American sporting history and famously his grandsire Nasrullah went on to win the Triple Crown in 1977.
5) Red Rum: Another famous Irish gelding, Red Rum is the only horse in history to have won the Grand National on three separate occasions, racing to victory in 1973, 1974 and finally 1977. Since the Aintree steeplechase is widely-regarded as being the ultimate test of a horse's stamina and courage, such an accomplishment means Red Rum will forever be seen as one of the all-time greats.
In fact, his 1973 comeback victory, in which he made up 30 lengths to win the race, is considered one of the greatest sporting achievements in history, with Red Rum's remarkable run memorialised with a statue of the horse at the famous Liverpool racecourse.
6) Frankle: A modern legend, Frankel went unbeaten in 14 races, retiring as the top-rated horse in the world in 2011. Some of the stallion's career highlights included winning the 2,000 Guineas by six lengths and romping to victory in the Queen Elizabeth II Stakes at Ascot.
Even when he went from racing over a mile to racing over a mile and a quarter, Frankel kept winning and signed off with stunning victories in first the International Stakes and then the Champion Stakes.