After consulting his vet and the horse's owner Max McNeill, King said in a statement: "Mille Chief is getting better and we can see improvement.

"But we have basically run out of time to make the Triumph Hurdle. You can't go half-cocked to Cheltenham."

Alaivan, trained in Ireland by Edward O'Grady, is the new favourite.

Mille Chief had been as short as 4/1 to win the race for four-year-old novices, and had been touted by King as one of the best horses to have passed through his yard in Wiltshire.

A winner of four of his last five races, a sequence only broken when he was brought down by another horse at Market Rasen, he was particularly impressive in his most recent outing, winning by six lengths on soft ground at Huntingdon with 13 rivals beaten fair and square.

King remains hopeful his horse will return in time for the festivals at Aintree and Punchestown later in the spring.

But punters will switch their attention to Alaivan, a 17-length winner at Fairyhouse last time, and another Irish raider with some impressive statistics, Carlito Brigante.