Nationalism, money, conceit: often the ingredients for disaster, but on Saturday, March 7th, 1964, this was the background to two racehorses who were each considered unbeatable.

Arkle and Mill House provided National Hunt racing's greatest head-to-head and in the process illuminated the sport to a usually uncaring greater public. As theatre it was riveting, but as sport it provided the ultimate. Arkle emerged as probably the greatest champion the game has seen and certainly its most evocative. In Ireland he became both a hero and a symbol rolled into one, proof of the hold the thoroughbred racehorse has on so many.

The omens were hardly obvious, though, immediately after the Duchess of Westminster bought a three-year-old in 1960 for 1,150 guineas and asked Tom Dreaper to train him. Arkle, named after a mountain facing the Duchess' home, was beaten in two bumper races before winning his first race at Navan in January 1962.

That was over hurdles, but over fences Arkle was a revelation, winning easily at Cheltenham 1963 and setting himself up as a likely challenger to that year's brilliant Gold Cup winner, Mill House. Arkle's rider, Pat Taaffe, had been on the giant Mill House in his first two races in Ireland, and, after the horse was sold to be trained by Fulke Walwyn in Britain, he told his colleague Willie Robinson: "You will soon be on the best horse in Britain and quite possibly the world."

When Arkle emerged, Taaffe changed his mind, but no one in England wanted to listen. Still only a six-year-old when he won the Gold Cup, Mill House was already being compared with the five-time Gold Cup hero Golden Miller. The possibility of defeat was nigh on laughable.

That view seemed to gain credence when Arkle and Mill House first clashed in the 1963 Hennessy Gold Cup at Newbury. Mill House conceded 5 lb to the young pretender and beat him by eight lengths. Yet in the process Taaffe discovered how he would turn the tables at Cheltenham.

In a later interview, Taaffe said: "Losing to Mill House at Newbury was so important. I knew Mill House was a heck of a horse, a born jumper. He could stand off at a fence and still get over them easily. Yet I let my fellow jump with him in the Hennessy and, of course, in the end he slipped up on landing over the third last and we lost the race. But I knew we could murder Mill House for speed, so I decided to beat him between the fences."

So it was in March that two horses, two camps - and, it's not totally fanciful to suggest, two nations - squared up over the historic Cheltenham course. Two other horses lined up, including the 1960 Gold Cup winner Pas Seul, but they didn't count. Mill House was the 8 to 13 favourite, Arkle was 7 to 4. In hindsight it was a price from the gods. With a small field, Robinson made the running on Mill House while Taaffe and Arkle bided their time. Arkle pulled for his head initially, but was jumping well in contrast to Mill House who fiddled some of the early fences and then startled the crowd by getting right under the ditch with a circuit to go.

If anything, however, it seemed to wake the slumbering giant. Mill House stretched going down the back straight and opened a gap. Arkle would have to be everything Taaffe and Dreaper believed him to be to catch Mill House. He was and then some.

Closing steadily, Arkle had ranged to within a length by the third last. Mill House sensed him and threw a colossal leap. Arkle matched it. Mill House's supporters must have felt queasy with impending doom. The huge Irish contingent simply opened their mouths and roared.

Robinson's whip rose as the pair approached the last. Mill House put his head down and heaved one last effort but Arkle had too much. Touching down after the last, the Irish-trained horse sprinted up the final hill to win by five lengths and break the track record by four seconds.

Arkle and Mill House met three more times with the Irish horse winning every time, including a 20-length victory in the 1965 Gold Cup. Arkle's big race tally also included, among others, the Irish Grand National, the King George and the Whitbred, and his superiority over his peers was such that the "long handicap" system had to be introduced to give the others a chance.

March 7th, 1964, however, remained his most evocative day. The day when Arkle really was unbeatable.